Because the GOP did not take seriously election irregularities in the 2020 election introduced by mass mail-in ballots, they treated voters and ballots as equivalent in nature, and confidently assumed polled projections from voters would neatly project onto ballots.
Unfortunately for the GOP, the nature of these two classes of vote count determinants, voters and ballots, couldn’t be further apart. One is an individual, often a very stubborn one with feelings, thoughts, and opinions, and the other is an efficient collectivized harvesting operation in low-friction communities.
With the loss of many gubernatorial and state legislative races in swing states, the path to solving the problem of harvested ballots is now closed, and the GOP will have to face this reality and engineer their own ballot harvesting operation as a solution if they ever expect to win another election.
In hindsight, this is what the GOP should have done in the first place, but they are the pearl clutching “law and order” party, and asking them to violate their principles or their values is itself a monumental task.