The minimum age requirement to serve as a senator is 30. The average age of the Senate is currently more than twice that. While there is certainly a lot to be said for institutional knowledge and experience, Congress looks less and less like America and more and more like a (very white) old person’s retirement home every session. Given the opportunity to safely support someone who is younger and more proactive in their support for left-wing initiatives (as opposed to Feinstein, who has largely been reactive in embracing the platform being pushed by younger Democrats) when there’s now absolutely no chance of spoiling the race and accidentally ending up with a Republican in that seat, why not take it?
Further, to your point that one party is populated by actual monsters: Feinstein has been more willing than most to try and find common cause and compromise with them. And again, while there is much to be said for compromising with your political opponents to accomplish your goals, this is demonstrably not one of those times. (She’s started to change her tune and has been voting against Trump’s nominees more frequently lately, but there’s no reason to think she’d have done that if she weren’t suddenly facing the prospect of actually being held accountable by the people of her state.)
