The election is 4 months away... he’s got to start advertising sometime.
I can’t imagine anyone who voted for him last time changing their mind, and I personally know many democrats who have said they’ve had enough of their party and WERE happy with the economy under Trump, and see the Dems as at fault wasting 3 years.
That is probably correct. I am willing to concede that. However, it is very likely that people who sat on the sidelines against Hillary are coming out very strongly against Trump. Just reiterating what was said above, it seems very likely that the polls are correct. If I had to make a prediction on an election held today (as reflected in the polls today), I would bet that Biden will rout Trump in Electoral Votes.