At one former employer, I literally was the best worker in the group -- I got the highest ratings possible from the interim manager who had been working there for years, and the highest ratings from our division chief above him. Then we hired a new manager, and I quickly got the lowest ratings. And lots of other top people in the group suddenly left around that time, too.

So, this kind of shit really does happen, at least to some of us. Some are smart enough to leave the sinking ship before it tanks their career.