Mainly to the extent that they fully underestimated Donald Trump in 2016, and had not ramped up the fraud machine adequately that year. We were so lucky that we got to experience MAGA for his first term.
i believe 2016 was rigged to a minor extent as no one expected the appeal of DJT. and by the time polls were showing it, it was too late. but they tried to get things going, it just wasn’t enough... the pandemic allowed bigger plans and the collusion of bipartisanship sealed the deal.