This is just a guess, but the article from the Crimson that was from the plagiarism voting board that said Gay's work would have clearly been "voted" for suspension, probably did her in.
The board was already pretty close but chose to retain her before this, but their position became less tenable when this letter was published. The letter itself bears close reading, as it's a wonder of rhetorical skill. Really, anybody who wants to effect change should read this letter and learn from it.
https://www.thecrimson.com/article/2023/12/31/honor-council-...