Trump can be a good speaker when he wants to.
However, most of his quick speeches for the press are bigly simple. He repeats the same thing multiple times and slightly rephrases them occasionally. Kind of like they shout the same variations of the same questions at him. No one listens to the whole speech anyway, they hear the sound bite from CNN or Fox. So might as well repeat the same thing 5 times.
In speeches that are given for the people there he uses two kinds of speeches. The thoughtful speech like the one I linked, and the âdo it for the Gipperâ speech. And only in one of those are you going to find any sort of complete erudition.