The reason they lost is far simpler.
1) She is a woman, the US still does not have the ability to support a Female president
2) She was hand picked by the current establishment she did not win the primary and probably would not have won the primary.
If the Democrats had run a primary without Joe Biden and selected a candidate that was male they most likely would of won.
This type of excuse is an example why the DNC lost. It is called DEI. DEI is where you pick people, for tough jobs, based on a shallow criteria; shoes size and curly hair, that have nothing to do with competence needed for the job. It tries to make hard reality, into a TV show, where any actor can play any role, since it all about scripts, directors, producers, actors, and not actually about doing a very specific job in reality. An actor can play the role of an inter galactic warrior who has not yet been type cast.
If the Harris had been a genuinely competent person, running for President, her sex would not have been the issue. She also had a tough situation having been placed in the position of running, with too little time. However, that was all due to the TV show that hid the decline of Biden and made it about an him being a elderly DEI "acting" president, that suddenly had to deal with the hard reality of the job. That could not be covered up, and lied about, to maintain the made for TV illusion.
Trump is more competent, based on his first term performance, in reality, with the same the issues he was still pursuing, that Biden and Harris had messed up, due to bad advise from far Left producers, writers and directors. All the common sense people saw that and voted for Trump. Those who live by TV and Hollywood principles, got caught up in a fantasy world. A little less than half of the USA have fried brains, due to too much emotional thinking; right brain, and not enough reason; left brain.
DEI and the resultant incompetence, even in the highest places, is why the DNC has to lie, cheat, censor and even brow beat. They assume good acting and a lots of funding from rich donors is all they needed to win. Those who voted for Trump wanted free markets, freedom of speech, less big brother regulations, and to be liberated from the con job of the TV show of incompetence. Trump used 1/3 the money as Harris, got more votes due to his competence and his better understanding of the reality needs of the majority.
Emotional thinking can be useful, since it can access a situation quickly. However, both reality and fantasy use the same emotions and emotional assessments can be the same for both, making it harder to separate reality from fantasy. You can have Broadway play of a small starving child, getting you sympathy, or you can go outside and see it in the streets and feel the same way. The Left seems to confuse where th door of the theater begins and ends due to too much emotional thinking training; actor training. The rational person can still feel empathy both ways, but can better assess the emotional doorway between reality and fantasy.
Trump derangement syndrome; TDS, was not about the reality of Trump, but the theater script from the directors in a play, with emotional thinkers confusing where the doorway between reality and fantasy started and ended. Many underestimated Trump due to not seeing the real person but the person created by the DNC theater company; DTC.