You’re not wrong, but the comparison I like here is Ruth Bader Ginsberg. She wasn’t just doing her job well, she was one of the best Supreme Court Justicies EVER.
She didn’t resign when the time was right, and as a result she died under Trump, a republican got her seat, and all the great things she did were swiftly demolished, wrecking decades of work over one single mistake: Not knowing when to step down.
Now I know the situation isn’t perfectly comparable. But if Trump gets in, then every good thing Biden has done will be swiftly undone. This was a hellish dilemma, but if Biden wants to do his job well, he needs to do that by not letting Trump into the White House again.