Do I have to provide proof? Or can I just have a hunch like we all do for the 2020 elections?
We have a very decentralized voting system, as has been stated already in this thread. Democrats don't control that system, so if they've figured out how to cheat, it's not because they somehow had more power over the voting process than the Republicans.
With the exception of a a few statistical outliers, voting done in red counties is officiated by red officials and voting in blue counties is done by blue officials.
My personal belief, that I have no better proof than any of the evidence already presented here by others, is that both sides are gaming the system and covering it up as best they can by somehow pumping numbers up to favor their candidate. They need to avoid scrutiny, so they can't just cause a historically red or blue state to massively flip without a good narrative. Hence why California isn't worth anyone's time to cheat any time soon, but those battleground states are very popular.