I'm inclined to believe that it's because you can simply bribe him to change his mind. He's a convenient idiot puppet with power and you can tug on any string to get him to do things you want him to. It's probably why TACO. There's probably a bribery match going on in the background.

It he was a zealot of his beliefs, rigid in his thinking, I believe he would be put down. But he's so malleable, so it's more useful to people that have the option to assassinate to bribe instead.