Yeah, they'll alienate the voters who never cared before but that Trump pulled out of the woodwork. On the other hand, they might bring back some moderate conservatives who would be willing to vote for a Republican that they think might be ok but not willing to vote for Trump. People who grudgingly voted Biden in 2020 but wouldn't if there had been almost any other candidate. People who didn't bother to turn out in 2020, or skipped voting for Pres, or wrote in, or voted third party.

Which one of those groups is larger? I have no idea. But I'm not convinced that the Republicans automatically lose if they get rid of Trump. He certainly galvanized a big portion, but he alienated a big portion as well.