Great retrospective, and apart from the personal burnout story, could be titled "what happens to a startup when managers start to run the show"
I think people mistake “manager” as being people without tech skills. I think a tech company should have managers to create alignment and those managers should spend part of their time “managing” and part of their time still honing their tech skills.
Of course clueless managers and extreme bureaucracy will destroy a company, but I very often see engineers that just want to do X and ignore everything around it as if they were working in a isolated environment. It's often the managers calling these engineers back to reality, which creates tension.
On the other hand, there are plenty of managers that do not know how to manage people, that do not even know what is expected of them. Should they optimize for cost? For productivity? For employee happiness?
Competent managers are a minority. They tend to rise quickly, leaving the inept ones to run the day-to-day.