Well, he's given himself lots of practice. He loves his rallies.he has decent projection
You all have probably never paid attention to it, I have... notice how he always uses the same mic at all his rallies. That's because the way a given style of mic pics up your voice is unique to that model/brand of mic. You learn to work the mic with the angle of the center-line of your voice. Watch how his head moves in relation to the mic when he's doing a rally, especially at the end when he does his closing with the maga spiel. He works it, and I bet if you watched several rallies, his head movement would be a carbon copy at each rally when he does his close.