Without a conviction, SCOTUS have got to decide for themselves whether he's guilty of insurrection, haven't they? My guess is that once they've weighed up all the evidence and read the constitution again, they'll decide that putting him on the ballot is the outcome that is less likely to get them shot and go for that.
Regarding winning clearly - with a republican majority in the house, I don't think it's clear, at all, what will happen if they have to ratify a Biden win in January. Seems more than likely they'll thrown out however many of his close wins they need for Trump to win.