Why does Trump keep [trolling the libs] about a 3rd term?

Because he knows the media is full of Teh Stooopid and they'll dutifully imply that he wants to become emperor

Well, you gotta admit that he has shown himself willing to commit to some of his more outlandish things.

When he first started [trolling the libs] about Greenland, lots of his supporters (including you) felt that he didn't really want Greenland. That it was just to achieve some other thing. But it turns out, no, he wasn't actually trolling the libs. He's genuinely dead set on getting Greenland. He has identified it as a genuine national security goal and is really, seriously pursuing that as a policy - and says so frequently. So I think that we're all kind of required to take all this stuff seriously, because Trump is perfectly willing to actually pursue policies that even his supporters think he's not actually going to follow through with.