They didn't vote for Biden, they voted against Trump. Just like they voted against Hillary last time. I'm sorry you can't see that.
it's the same as Hillary. many nonvoters came out in 2016 to vote against her. same here, except that I think you also saw many Republicans who were willing to take a chance on Trump decide he was too much this time, especially compared to basically Republican Joe. they didn't believe he was the spearhead for socialism, and have been proven correct so far.