Happened when management started treating the IT department like crap and demanding we work overtime with no extra pay. Almost all the experienced developers left in the spam of a year.
Before I left, I told them they would never be able to assemble such a good team again.
Four years later and they are still struggling to keep the department running, according to a friend that chose to stay. The few developers they are able to hire are either terrible or quit after a while.
I get the feeling the same will happen in my current job :/
We had something similar, but not only were we being treated like crap, we were basically told to be "yes men" and that we were all perpetually on call. And there were only 3 of us. No vacations, and I even had my VP calling me 2 days after having surgery done asking me to come back to the office, despite not being able to sit due to the nature of the surgery. That was the straw that broke the camel's back for me.
So I found a new job and put in my two weeks. Then my coworker got fired less than a week later for explaining that terminating all EC2 instances running our app would in fact cause an outage rather than just doing it. Within a week of that, my boss, the last guy on my team, up and left.
I'm curious if they ever got someone knowledgeable on how to run the ship on board after that. Last I heard, the entire office I had worked at was shuttered during COVID.
Over the years I've come to the conclusion that good managers in general are rare and the few good ones don't go far in their careers because big companies favors backstabbing psychopaths and narcissists, just like in politics.