Because if you aren’t the bad guys then they’re just essentially the low level stooges of the evil mastermind just doing mundane evil shit for no discernable reason.
Where as if you’re the bad guy they’re virtuous principled people just doing what’s right (allowing them to have complete dominion over the moral high ground)
They would literally, unironically, genuinely lose 100 times to republicans before they elect anybody who would appease anybody left of Clinton.