If Trump wants to lose a whole bunch of GOP votes.
It's only potentially acceptable to let them off the hook after very long and very public trials that show how awful those people are.
You arrest them and immediately let them go, the Dems will say "ugh" and the GOP will say "ugh". Dems will say it's just partisan BS, because if there was anything there, the GOP would've gone for it, and we'd say they should've gone farther. We'd be united, not in the way that Trump would want.