It's a false flag operation. Trump realized that his tweets have become a political liability, so he had this done so that he can claim that someone hacked his account and posted all this weird stuff on it.

[Me takes off tinfoil hat.]

More seriously, what would the point be? Stock price manipulation? Making users think about moving to another platform? Political? International espionage?

[Edit: Since everyone seems to have missed it, the part inside the "tinfoil hat" blocks was not intended to be taken seriously. I expected it to be interpreted as a /s, but apparently it was not.]