This doesn't make a ton of sense to me. The only way I see a faculty member leaving after an accusation like that and it truly having no merit, is if they saw toxicity in how they were treated by their colleagues. No attending leaves because of not wanting to interact with 1 resident. If that faculty felt abandoned and railroaded by the institution or department based on only those claims, then I could see not wanting to work there anymore.
On the other hand, I have seen plenty of people with absolutely egregious behavior decide to resign or "retire" after "no wrongdoing was found" following accusations.
I have been in this position with my prior employer. I can't go into details for obvious reasons, but I was always treated as guilty until proven innocent. I am in an interracial marriage with biracial children, and I felt strongly that I was being accused of racism with no clearance of me in the end. It was the most ridiculous and insulting situation I could have suffered. The resident involved faced no repercussions that I'm aware of, despite my early involvement of the chair and program director in the situation, and clear evidence and documentation I provided about the issues involved.
Ultimately, the resident was allowed to graduate despite clear ethics and knowledge concerns. I wrote that I believed the resident should have repeated my rotation with someone else because they didn't show up to most of my rotation (and never complained until the bad review came at the end), did not know the fundamentals of what I do, and ultimately they were allowed to have full research time (producing nothing). The program overrode my review and gave them credit for the rotation anyway because they would not have had enough time in clinic per ACGME to graduate if I had failed them.
All I got was "we cannot have accusations like this in our department," and I was sent to weekly mandatory hour-long counseling for two months. The topic kept coming up at every annual review as well. The institution prides itself on building a file on its faculty members so they have cause to let anyone go at any given time.
This was not just me that things like this happened to. Several other faculty I'm aware of got caught in things like this as well. They encourage resident surveys to report every single little complaint no matter how trivial so faculty can improve, then they come down on faculty with weekly mandatory counseling for months and get put under a microscope for things as simple as "faculty texted me too many times" and "faculty kept me here until 7 PM" (I'm not exaggerating). "We cannot have anything but perfect resident surveys."
The culture at that institution was so incredibly toxic, it's hard to even explain or imagine until you've experienced it. Turnover was high, resignations were rampant, and they just pull new grads and unsuspecting junior faculty to replace them. The residency interviews are tightly controlled with a small number of residents and faculty involved only in group settings to ensure that nobody talks honestly and they fill after several years of going unfilled. Now that I'm out after 10 years of abuse it's hard to even explain it to people without them thinking there's something wrong with me.