Because we is Commiefornia, and we hates her, we does.
Kevin de Leon is to the left of her, and received close to, but not quite, the % necessary to win the outright endorsement of the California Democrats.
De Leon is significantly behind Feinstein in the polls at the moment, but there is hope. She still has the upper hand because the Senate race will be between her and de Leon, and Republicans will probably all vote for her since she’s basically a Republican, and no Republican is going to qualify for the final ballot anyway.
But…the answer is, she is a fucking Republican, and that’s why we hate her.