....al Bagdadi was the self proclaimed caliph, and he was the head of their recruting organization. In the extreme circles, he was also considered to be immortal. Trump's words were clearly meant to undermine this. These were intentional words that you take as "typical trumpisms" - they are not.
They are calculated words. Because you dislike trump so much, you consistently underestimate him. To accomplish what he has in life, he is most certainly a master manipulator of people (look how he gets you jumping all over the place over magic marker on a weather map).
What is also interesting to me is that al Bagdadi was in western Syria. Clearly, he saw a potential opportunity for recruiting in that area since Trump pulled back (I do consider that to be a mistake).