Bibi's number one priority is supporting whatever helps Bibi stay in power and throwing everyone else under the bus, Trump learned that the hard way last November.
Likud would win easily without him as the head of the ticket, the reason Israel keeps having endless elections and their governments keep collapsing is nobody wants to work with, or be part of a government that Bibi is "in charge" of, ESPECIALLY when he's under indictment.
I don't think Likud would replace him with anyone "more conservative", and possibly we'd end up with someone LESS conservative, but by the same token, I don't think there would have been much difference at all if Bibi had been defeated by "opposition leader" Benny Gantz in 2020 either. They seemed to agree on 90% of the issues overall, their loathing of each other appeared to be personal. And quite frankly, Gantz should have trusted his instincts in being dead-set against joining any government with Bibi in charge, given what happened after he did so.
I agree I think he is probably holding his party back rather than winning votes on his personal popularity but I’m no expert. He’s been in charge forever.