A politicians job during a campaign is to convince people they are worth electing.
Harris lost the electoral college and the popular vote. Harris failed to convince a majority of the electorate that she was worth voting for. That's it, that's the whole story: she failed to win over voters, and failed to rally support from her own party.
She became Biden 2.0 as her campaign went on, and people didn't want four more years of Biden. She showed no meaningful difference between the current administration and her own should she win.
She lost Michigan by less than 100,000 votes. More than 100,000 people protest voted over Palestine during the primaries there. Harris took that information, and doubled down on Biden's policy, ignoring her constituents. The DNC welcomed numerous Republican officials to speak at the DNC, the same officials who helped Trump during his first presidency, they were welcomed with open arms. But no Palestinian Democrats, including those put forward by the Uncommitted Protest Vote Movement, were given time to speak at the DNC.
And as her campaign went on, she proved that was more concerned with trying to win over Republicans (like Hillary failed to do in 2016, and Biden failed to do in 2020) than she was trying to rally support from her own undecided voters and non-voters. Less than 40% of eligible voters vote, so her strategy was completely write off the 60% that could he won over, and focus on trying to win conservatives, which required more Centrist policies, which just alienates progressive Democrats...
Anyway, let's see, oh yeah: 94% of registered Republicans voted for Republicans in 2024, the exact same amount as 2020.

No one was duped, you sound weird and strange talking the way you do. It's off-putting and makes me want to actively work against Democracy, because you're doing exactly what I've been describing: dismissing everything I have to say while condescendingly speaking to me like I'm some misguided child.
You need grow up and accept that the Democrats fucked up, backed the wrong strategies, and were significantly more unpopular than they thought they were.
It is sad how quickly and easily you've fallen for the fallacy that it's not party leadership, but the voters they're supposed to represent and reflect that are the reason why Democrats can't fucking win. Absolutely delusional.