Yes they are elected, but largely incumbents in safe seats, and no one forces any of them to be ranking committee members. "It's my turn" is not actually a good reason for someone to have an incredibly important job.
No I don't think any of them have a magic "stop Trump" button, but the party instincts lean towards conflict avoidance. More than that, they are very hierarchically inclined and tend not to look kindly on junior members who get a bit more aggressive. You can argue that Schumer and Jeffries shouldn't be attack dogs, but they also tend to discourage anybody else from doing it. If more junior people go out on a limb, there is a reasonable chance the leadership will saw it off.
I saw this a lot in the Bush era when junior senators were, like, Dick Durbin.