On the issue of Walker, we must recognize that two moderate Republicans were beaten by the Democrats two years earlier. His opponent, Rafael Warnock, certainly had character issues. When we look at the general election vs. the runoff, Warnock increased his margin from 38,000 to over 99,000. The reason there was a runoff was caused by a Libertarian Party candidate receiving 2% of the vote. Those voters would either have not voted or supported Walker, who would be closer to libertarians on economic and limited government issues. So what happened? Warnock's runoff numbers declined by 126,000, while Walker's declined by 187,000. Either the Democrats cheated or they did a better job getting their voters to the polls.
My bet is on the former. This Senate seat assured Schumer would be majority leader in 2023. It was too important to lose. Walker did underperform vs. incumbent Governor Deal. Now whether that was due to country club weenies and soccer moms not liking Walker or the Democrats at the national perhaps not wanting Stacey Abrams is a question.