"Voters in liberal strongholds across the country, from city centers to suburban stretches, failed to show up to vote for Vice President Kamala Harris at the levels they had for Joseph R. Biden Jr. four years earlier, contributing significantly to her defeat by Donald Trump,” the New York Times reports.
“Counties with the biggest Democratic victories in 2020 delivered 1.9 million fewer votes for Ms. Harris than they had for Mr. Biden. The nation’s most Republican-heavy counties turned out an additional 1.2 million votes for Mr. Trump this year, according to the analysis of the 47 states where the vote count is largely complete.”
“The drop-off spanned demographics and economics. It was clear in counties with the highest job growth rates, counties with the most job losses and counties with the highest percentage of college-educated voters. Turnout was down, too, across groups that are traditionally strong for Democrats — including areas with large numbers of Black Christians and Jewish voters.”
Your numbers don’t show that it’s vote by mail. Kamala lost ~ 13% compared to Biden nationwide and in your example vote by mail state Oregon she lost ~14%
California isn’t in yet but doing some rough math she looks like she’ll get ~9 million total compared to Biden who got over 11 million, so around an 18% drop in another very heavy vote by mail state.