In my last job, requirements, such as they were, were based on some idea that someone in authority thought we might need. No consideration was given to the needs of the clients of the code. They weren't savvy in the any of the current technologies, so it wasn't even the latest fad.
I developed the skill needed to implement their dumbfsck idea-du-jour quickly and without breaking existing code. However, the resulting code was increasingly more convoluted and incomprehensible. I had inherited a god object that I only added to over time.
When I quit, my boss knew he was not going to find anyone that could keep up my pace, much less understand the code. He tried to get me to stay, but I told him that I will never work on this code again, so there'd be no point in staying.
A couple years later a former coworker told me that the guy that had taken over had a bug in some code that was convoluted but rock solid when I left. I figured he had noodled with the code and broken it. Sucks to be him.
Told my coworker to tell him that my advice it to look for another job.
So yes, I hear you when you say they're perfectly capable of sabotaging themselves.