Is there a link for me to read more. Why is he in power. Didn't someone quit? Why is he "acting" president?
Ok, it's a bit late, but just to make things
somewhat clear...
It is because he betrayed Dilma by swearing allegiance (or whatever similar you call it in English) to the opposition and he's planning to introduce a series of completely "anti-popular"/neoliberalism-oriented politics by bastardizing the Constitution.
While Dilma is definitely NOT a good president, the impeachment process is not quite 100% legal. In fact, in early June, a leaked audio by then Minister of Planning Romério Juca pretty much confirmed what was suspected: it is basically a conspiracy to overthrow Dilma in order to, uh... suppress the Lava Jato Operation (you guys are calling it "Car Wash", I suppose) led by the Polícia Federal (the brazilian equivalent of the FBI).
In a twist act of irony, it's also highly suspected that Temer himself is envolved with heavy corruption in the Car Wash Operation. Dilma, on the other hand, is not even under any investigation whatsoever. Does it raise you any flags?
Don't really know how to put it, to tell you the truth, since my English sucks. So deal with it. But that's what the whole thing is, in a nutshell.
Actually, it is algo bigger than the above Wikipedia link.
But hey, it borders on off-topic territory, so just enjoy the Olympics.