This isn't about Trump, really, but about the numerous (not all!) people who succeed in politics, in the US and elsewhere, because they have one set of skills (good showmen who know how to work the crowd, basically), but are absolutely incompetent at governing. Total dumbasses at best.
Basically, they're supposed to go out there and give the speeches and be the face and then hire the smart and competent (even if evil) people to do the real work and make the real decisions.
It's interesting that it never really works out that way.
