With one exception, every GOP Senate candidate running in a state Trump lost also lost. These included every closely contested state, too. The lone exception was Susan Collins in Maine, whose defining characteristic was her OPPOSITION to President Trump on many issues.
It will likely be impossible to verify this because exit polls are just as useless as pre-election polls these days, but I suspect Trump's influence over many down-ballot races was minimal at best. This wasn't a fault of his, but was simply a function of his appeal to many independents and old-school Democrats. A lot of these voters supported Trump but had no interest in the GOP in House and Senate races.
Look at West Virginia, for heaven's sake. Trump won there by his most lopsided margin in 2016 (and maybe 2020 as well), and yet there are more registered Democrats than Republicans there.
I do not disagree with your assessment up to a point. Ballot fraud and Ballot Harvesting is most effective when used to elect a Senator or President, possibly a Governor. It is less effective in smaller district races. It was effective in Cali House races in 2018 because the GOP was caught off guard. It was effective in Georgia and in PA.
Our RINO Senator is very unpopular in our state yet he just squeaked by as did Trump. But the mail in ballots here were out of control and had universities been actually in session they both would have lost to fraud and ballot harvesting.
You have to factor in a lot of things but do a comparison between Trump and Obama’s coattails. Rush was pointing out the attacks on Trump right now, even though he is leaving office, is the outright fear of his influence over conservative voters.