There’s a key distinction between the number of Biden voters who voted for Harris and the relative vote totals. Some of Harris’s voters didn’t (or couldn’t) vote for Biden. First time voters or Trump-Harris voters wouldn’t be Biden voters, so the number of her Biden voters would be lower than her total number of votes.
Did you look at your own numbers? Trump did better than he did in 2020, while Harris did substantially worse than Biden.
Substantially worse, but not 19 million worse.
Trump was +3 million, Harris was -6.
There’s a key distinction between the number of Biden voters who voted for Harris and the relative vote totals. Some of Harris’s voters didn’t (or couldn’t) vote for Biden. First time voters or Trump-Harris voters wouldn’t be Biden voters, so the number of her Biden voters would be lower than her total number of votes.