Cool but pop vote means nothing in presidential election. The missing Dems were all from states that don't matter thanks to the electoral college. Harris did nearly as well, or even better than 2020 Biden in the key swing states, and of the ones she didn't do better than 2020 Biden she could have done just as well and still been beaten by 2024 Trump, who got more votes in those swing states.
Since this entire original post is about the overall popular vote, when I said "did better" I meant in regard to number of votes in those states. But Trump did even better. My point is that the "missing Dem votes" illustrated from the OP were almost all from states other than the key swing states, and didn't ultimately matter due to the electoral college. In the key swing states, Harris got nearly as many or in some cases even more than Biden in 2020. Trump just got even more.
Michigan is the sole swing state in which Harris would have defeated Trump if she had gotten Biden's turnout in 2020. In all other key swing states, even with Biden's 2020 turnout, Harris would have lost to Trump's 2024 turnout. She still would have lost the electoral college.