Joe Biden didn't wake up one day and realize he'd been wrong for 30 years.

I covered him in the Senate, in the Obama White House, in the Democratic Party's post-Trump reckoning. Biden was rarely the voice calling for transformational change or go-it-alone ambition.

But you'd never know it from his presidency. The standard explanation for all this is the advent of the coronavirus. The country is in crisis, and Biden is rising to meet the moment. But I don't buy it. That may explain the American Rescue Plan. But the American Jobs Plan, and the forthcoming American Family Plan, go far beyond the virus. Put together, they are a sweeping indictment of the pre-pandemic status quo as a disaster for both people and the planet — a status quo that in many cases Biden helped build and certainly never seemed eager to upend.

Over the past few months, I've been talking to sources to better understand why President Biden is making such a sharp break with Joe Biden. Here are a few reasons:

The collapse of the Republican Party as a negotiating partner.

Most discussions of the renewed ambitions of the Democratic Party focus on ideological trends on the left. The real starting point, however, is the institutional collapse of the right. Before Biden, Democratic presidents designed policy with one eye on attracting Republican votes. That's why a third of the 2009 stimulus was made up of tax cuts, why the Affordable Care Act was built atop the Romneycare framework. Both as a senator and a vice president, Biden backed this approach. He always thought a bipartisan deal could be made and usually believed he was the guy who could make it.

But over the past decade, congressional Republicans slowly but completely disabused Democrats of these hopes. The long campaign against the ideological compromise that was the Affordable Care Act is central here, but so too was then-Speaker John Boehner's inability to sell his members on the budget bargain he'd negotiated with President Barack Obama, followed by his refusal to allow so much as a vote in the House on the 2013 immigration bill.

And it's impossible to overstate the damage that Mitch McConnell's stonewalling of Merrick Garland, followed by his swift action to replace Justice Ruth Bader Ginsburg, did to the belief among Senate Democrats that McConnell was in any way, in any context, a good-faith actor.

The result is that Obama, Biden, the key political strategists who advise Biden and almost the entire Democratic congressional caucus simply stopped believing Republicans would ever vote for major Democratic bills. And so Democrats stopped devising compromised bills in a bid to win Republican votes.

This has transformed policy design: These are now negotiations among Democrats, done with the intention of finding policies popular enough that Republican voters will back them, even if Republican politicians will not. Biden still talks like he believes bipartisanship is possible in Congress, but his administration has put the onus on Republicans to prove it. That, more than any other single factor, has unleashed Democrats' legislative ambitions.

A new generation of crises created a new generation of staffers.

I've been struck by the generational divide within the Democratic Party. Washington is run by 20- and 30-somethings who run the numbers, draft the bills, brief the principals. And there is a marked difference between the staffers and even the politicians whose formative years were defined by stagflation, the rise of Reaganism and the relief of the Clinton boom, and those who came of age during financial crises, skyrocketing personal debt, racial reckonings and the climate emergency. There are exceptions to every rule, of course (see Sanders, Bernie) but in general, the younger generation has sharply different views on the role of government, the worth of markets and the risks worth taking seriously.

I put this observation to Brian Deese, the 43-year-old head of the National Economic Council. Deese was a young economic policy prodigy in the Obama administration. Now he's the guy running the NEC, and he agreed that the new generation of staff members see the world very differently. "There has been a lot more work done to try to understand what the roots of economic inequality are over the course of the last decade, and openness to thinking about power and power dynamics," he told me.

Deese said that this has revived interest in ways to strengthen labor unions — the American Jobs Plan calls for the Protecting the Right to Organize Act to become law, which Richard Trumka, the head of the AFL-CIO, calls "a game changer" — and in industrial policy, where the government directly subsidizes various industries to guide the path of economic growth. This is a break with the economic ideas that dominated from Jimmy Carter's presidency through Obama's.

"The next generation of the economics profession is rebelling against its predecessors by being all about inequality in the same way that my generation rebelled against its predecessors by being all about incentives, and this is a good thing," said Larry Summers, who served as Treasury secretary under Bill Clinton and NEC director under Barack Obama.

Biden has less trust in economists, and so does everyone else.

Obama's constant frustration was that politicians didn't understand economics. Biden's constant frustration is that economists don't understand politics.

Multiple economists, both inside and outside the Biden administration, told me that this is an administration in which economists and financiers are simply far less influential than they were in past administrations. This partly reflects Biden himself: he's less academically minded. But it goes deeper than that.

The core of this story is climate. "Many mainstream economists, even in the 1980s, recognized that the market wouldn't cover everyone's needs so you'd need some modest amount of public support to correct for that moderate market failure," Felicia Wong, the president of the Roosevelt Institute, said. "But they never envisioned the climate crisis. This is not a failure of the market at the margins. This is the market incentivizing destruction."

Deese, the NEC head, is notable for being a climate wonk who's now in charge of the nerve center of White House economic policymaking. And the scale of the climate disaster, and the speed at which it must be addressed, simply demands a different role for the government. "If you think across the big systems in our country — the transportation system being one, the power and energy system being another — in order to actually solve climate change, we're going to have to transform those systems," he told me.

Even beyond climate, political risks weigh more heavily on the Biden administration than they did on past administrations. This is another lesson learned from the Obama years. The Obama team had real policy successes: They prevented another Great Depression, they re-regulated the financial sector, they expanded health insurance to more than 20 million people. But Democrats lost the House in 2010, effectively ending Obama's legislative agenda, and then they lost the Senate in 2014, and then Donald Trump won the White House in 2016, and then Democrats lost the Supreme Court for a generation.

Many who served under Obama, and who now serve under Biden, believe that they were so focused on economic risks that they missed the political risks — and you can't make good economic policy if you lose political power. The Biden team is haunted by the fear that if they fail, a Trump-like strongman could recapture power. This helps explain why, for instance, they're unmoved by arguments that the $1,400 stimulus checks, though wildly popular, were poorly targeted. As one of Biden's economic advisers put it to me, "if we don't show people we're helping the dickens out of them, this country could be back to Trump way too quickly," only he used an earthier word than "dickens."

Biden is a politician in the truest sense of the word.

Biden sees his role, in part, as sensing what the country wants, what people will and won't accept, and then working within those boundaries. In America, that's often treated as a dirty business. We like the aesthetics of conviction, we use "politician" as an epithet.

But Biden's more traditional understanding of the politician's job has given him the flexibility to change alongside the country. When the mood was more conservative, when the idea of big government frightened people and the virtues of private enterprise gleamed, Biden reflected those politics, calling for balanced budget amendments and warning of "welfare mothers driving luxury cars." Then the country changed, and so did he.

Even when Biden was running as the moderate in the Democratic primary, his agenda had moved well to the left of anything he'd supported before. But then he did something unusual: Rather than swinging to the center in the general election, he went further left. And the same happened after winning the election. He's moved away from work requirements and complex targeting in policy design. He's emphasizing the irresponsibility of allowing social and economic problems to fester, as opposed to the irresponsibility of spending money on social and economic problems. His administration is defined by the fear that the government isn't doing enough, not that it's doing too much.