Earlier quoted context omitted.
No job is interesting enough that I would tolerate targeting and succeeding in firing a productive employee for internal politics. Doubly so if that behavior is coming from a department nominally in a support role. That's a dog to be put down.
There was probably other factors. Good pay/conditions/close to home/etc. Also it's not always so easy to up and quit every time someone looks at you the wrong way.
Deciding to leave doesn't mean put in your notice. It means look elsewhere. Leaving a job without another secured is always precarious absent a nest egg.