I never believed the Big Lie and, to be honest, I don't know any Republicans that did. I think it's hard to deny that the unique aspects of the 2020 election with its unprecedented number of mail-in ballots, ballot integrity processes reportedly watered down in some areas, increased workload on state election officials, combined with the inflamed rhetoric about it being our last chance to save democracy provided both the motivation and opportunity for fraud to occur. Plus, you have things like election officials in Pennsylvania changing election laws without approval of the state legislature as required by the Pennsylvania Constitution.
The mantra has always been "There is no evidence of massive fraud enough to have affected the outcome of the election". But, how much fraud is too much? Maybe the Presidential election wasn't affected. Perhaps it was only a Senate race. That couldn't have that much of an impact, could it?
Flash back to 2008 and the ongoing recounts in Minnesota for Senator. We watched the lead of Republican Norm Coleman slowly evaporate to favor Democrat Al Franken. Franken was eventually declared winner and became the 51st vote in favor of Obamacare when Coleman would have surely opposed. Later analysis indicates the probable number of felons illegally voting in the election far exceeded Franken's margin of victory. With most felons probably supporting the "soft on crime" Democrat Party, they most likely voted for Franken.
Even a little voter fraud can have a profound impact on the country.