I feel your pain about what happened. I've seen comparable things a few times first hand. My learning was: just leave once the change starts, only stay if you're getting something out of it. It's not my company, I'm only in charge of my life, I'll find something better soon.
I think I would not recommend to run once PE is mentioned, it can also change for the better, but it can be a red flag to look more closely.
This doesn't make it any better for the, you know, entire rest of the company.
It's important to remember that this startup industry relies on selling dreams to idealistic young grads who will usually end up under the bus while the higher-ups walk away with the profit, if there is any. And a lot of us here are complicit, because we rely on cheap labor and false promises to get the next company off the ground.
Once you see your first exit where the CEO walks away with $10+ million and every single other employee's stock (even the first few engineers) was made worthless in backroom dealings, you get jaded about the way this entire business operates.
PE fucks up everything most of the time, hurts the majority, and I hope I never encounter it again in my working career.
Usually if a company fails, it happens in slow-motion. As an employee you can often spot that years before it makes the news. Just move on before it makes the news.
Its been a while but it still brings out some bitterness. I did leave after an year but the damage had been done by then.
As a customer, rather than an employee, that's what I learned too. If a PE firm buys a company that I do business with, the best thing for me to do is to stop doing business with them.