What do you suppose prompted this tweet? Is he fishing for drama? He behaves like a little kid, pushing the boundaries as far as he can.
You didn't ask me but I'll give you my opinion: he has a shallow and populist ideology, which is based on many of the things one can hear among somewhat less informed social-right-leaning people. Like birtherism, flag-burning, VA bad, islam, walls for illegal aliens, and "federal" money should be spent on the "right" things. (Not that those things are necessarily wrong.)
Being a narcissist, he feels the need to be adored, and the shallow, fear-based, LIV, social right group is willing to give him that. So, much as you or I feel hungry at lunch time and thirsty after mowing the lawn, he gets that needy feeling and tweets. I eat a sandwich, you drink water, and he tweets and reads the adoring responses.