Like I said, I've been through this first hand.
I was exceeding expectations, and given a big promotion in the middle of it. But people I worked with and interacted with every day were feeling extremely stressed and worried about their ability to meet the new bar. Now, in many cases, they didn't need to be worried, but it's natural to question these things in an environment where you're seeing people get PIP'd and unceremoniously shitcanned regularly.
Morale was through the floor, it was an absolutely miserable environment to work in – even though I was personally doing quite well. So I said "fuck this" and was the first person out the door on my team. The second highest performer quit a week later.
The least technically capable person on the team was there for another year.