I don't think it's entirely out of the question that this was a CIA op, like the assassination of JFK probably was. Trump is treading on a lot of toes, after all- with the possibility of "peace with Russia" (not that I think he could succeed against the blob there), or the (also almost certainly unfounded) hysteria around "leaving NATO" (or extorting the other NATO members, anyways) as well as the fact that the Biden admin is absolutely guilty of a whole slew of crimes they don't want getting dug up.

Either that, or it was an unwell person, someone who hated him- he's a very hateable person TBH (though anyone with sense should understand, he's just as vile as the rest of DC regardless of party affiliation and if anything refreshingly incompetent/not with a death wish for his country).

The most obvious explanation as you said should be the assumption- but that this happened after he met with Orban (who for all his faults has been genuinely trying to prevent WW3, meeting Zelensky/Putin/Xi and then getting rebuffed by Biden before meeting Trump) stinks to me.