Every time you think the idiot manchild Donald Trump could not possibly come up with a way to be less presidential, the tax-dodging rapist sociopath burps up something else. It never ends, with this guy. He is incapable of being anything other than the worst person he can be.
What a strange, odd, petty little clod of a man. One way to approach this would be via the old stand-by: Let's just imagine, for a moment, what would happen if any Democratic president amplified the public statement "let them rot" about Republican regions of the country.
It wouldn't happen. For starters, most if not all prior U.S. presidents generally understood that their oath of office applied to all of the United States, not just part of it, and even the most paranoid of them knew better than to publicly broadcast any private feelings to the contrary. It was not until we got to this particular moment of fascism that the sociopathic leader decided to just ... not bother. Trump is so mired in petty revenge and retaliation he can't even muster the will to pretend to not be an overstuffed sack of garbage.
Then there's Trump's willingness to tie himself, still, to a "WalkAway" hashtag that was widely reported to be an obsession of Russian bot networks back in 2018. Does he … does he not remember that?
You might be tempted to feel a bit of sympathy towards Trump, theoretically in mourning over his own brother's death, but there's no evidence Trump actually is mourning, or in fact is doing anything but reading tweets and ranting at his television.