Well, either Trump is just really dump and ignorant and simply doesn't care about the implications of his tweets.
Or he does care, but just in a way that his tweets are aimed at two things:
- His followers, who get a boner about tweets like bigger button etc.
- The media and the establishment, who is getting hysteric.
Which in return is getting his followers another boner, because they love when media and establishment hates their messiah.
His tweets are just a reaction to what he sees on Fox.