It was going on before the ubiquitous mail-in voting of 2020.
2020 just allowed them to go for the gusto.
I have proven to my own satisfaction that this Democrat vote fraud is nationally directed, on a state-by-state basis.
There are different aims in every state - but it's coordinated from a central national location.
The RINOS just roll over and take it. I guess so long as they have their spots at the trough, they don't want to rock the boat. The RINOS are useful idiots for the Democrats. They put up enough token resistance to make it look good for the constituents back home.
The Republicans have ceded the inner cities to the hard left and their tactics. As a result, once red states have flipped blue because the fraudulent votes manufactured in the cities are now enough to flip entire state elections.