I think something similar, but I do not think that they made the mistake of accidentally rigging it for Trump instead of Biden. What I think is that the original plan was the fractional counting vote machines and they did set them up correctly, but even that was not enough because they underestimated how popular Trump was, so at a certain point when they knew defeat was inevitable they shut everything down, kicked out the people watching the count, covered up the windows, and pulled out their backup plan which was suitcases of fake Biden votes from dead people and nonexistent addresses.