I'm not sure when it all started going downhill, but there was a moment it was obvious: once the previous leadership team stabilized things a bit, the new CEO, the founders, and the investors started sacking everyone in C-level and replacing them with a bunch of yes people scratched from the bottom of the barrel. It doesn't matter what you've achieved, if you were promoted by the old team you are as good as dead. Worst part is that the new C-levels have barely any relevant experience to play the part beyond "whatever the CEO and the founders please". Some C levels were sacked very fast because they were strong voices while others played along with the CEO and prepared their exit leaving with full pockets and handing over their teams to those who will do the sacking (or encouraging people to leave).
If you think all this is high-level and irrelevant to you as a modest member of a team, wait until all that rains down rewarding the nodders and penalizing everyone else, lack of professionalism when making decisions, personal stories mixed with work, and thought censorship. There was a period of time that women dating managers got promotions. It even got to the point that two women were married to managers and promptly promoted way high in the company at the exact same time. Also don't dare to talk about unions, family needs, or issues with predatory co-workers who seem incapable of keeping it in their pants at work. Some employees are being put under "performance review" for asking the wrong questions, complaining about those topics or supporting those who speak up. Also happens to those disagreeing on something that they know more than the manager about. Literally, if you thumbsup the wrong comment on Slack then People Experience team will keep it on their list of reasons to fire you and they will tell everyone that you are toxic. With all this lots of great people with real knowledge left so definitely not a great place to work or grow professionally anymore. Never again a fancy startup if I can avoid it.