I'm only commenting about how Harris got dropped into a difficult place three and half months before election day. I think everyone can see her campaign strategy has been trying to find its footing since the initial euphoria wore off. However, Kamala still might win.
No one is saying Trump is a great orator. He simply knows how to push the buttons that make the opposition perform poorly with the voters it needs to attract.
If I follow Trump's rise, I would suggest he exploits the Democrat's current weakness as a political force. It simply represents too many ideals that don't fit well into a basket. So Trump doesn't win elections, but rather Democrats lose them with their platform and ineffective candidates. Biden wasn't exactly a big winner and certainly COVID helped his campaign.
My argument is further reinforced by the fact that the Republican party also has limited success, but the Democrats in their current constitution can't definitely put the Trump Republicans away. So everything you have said about Trump might be true, but it doesn't go far enough to honestly explain the Democrat's limited appeal.