In addition, as a salesman Trump thinks in terms of deals and lives in the moment: if you do this now, I’ll do that. Commitments, treaties, alliances, long-term relationships, honor… all those things are meaningless in the moment: it is all about this deal, and now. And because of this, he is fundamentally untrustworthy: when the time comes to hold up his end of a deal, it’s another moment and another deal.
Trump is Predictable… despite being Unpredictable

In short, he’s a Ferengi.