Michigan State University’s board of trustees and its embattled president have finally confronted a truth they have been reluctant to embrace: Lou Anna Simon’s tenure as leader of the institution she has presided over for 13 years has come to an end.

Simon announced her resignation Wednesday night, in a letter posted on MSU’s website. Earlier in the day, a second trustee had called for Simon to step aside, and the board has been discussing who might lead the university after Simon, the Detroit Free Press reported.

Precisely when Simon’s position became untenable is debatable. Was it when the Indianapolis Star first reported molestation allegations leveled against former MSU physician Larry Nassar by young women he had treated as the team doctor for USA Gymnastics? When the Michigan House of Representatives, and legislative leaders in both parties, joined the legions demanding her resignation? When viewers around the world were transfixed by the sentencing hearing in which Nassar’s victims confronted him and the university that enabled his reign of terror? When a judge sentenced Nassar to 40 to 175 years behind bars?

But that argument has become an academic one, overtaken by MSU’s urgent and undeniable need for new leadership.

Simon’s departure is an important first step. But it can’t be the last. (Michigan State athletic director Mark Hollis announced his retirement Friday, after this editorial was published.)

At MSU, “who knew” is one question — “who should have known” is another. Nassar abused at least 150 girls and young women over decades. The university seems to be taking pains to cast Nassar’s crimes in isolation — a Nassar problem, not an MSU problem. After an internal investigation, the university said no report was produced, thus nothing could be released.

The school owes its community a thorough accounting of complicity, or willful ignorance — in the school’s athletic department. To restore the university’s reputation, that’s the first task Simon’s successor must take on: an honest, if painful, audit of the school’s culpability, a process that must result in public findings.

Simon survived longer than most observers thought she would, backed by all save two members of the school’s board of trustees. This is not to her credit.

MSU has a lot to answer for. And a lot of work to do.