There is all kinds of public evidence of collusion, just because they decided not to charge a sitting president is hardly exoneration. But, the reason why you can still be guilty of obstruction even if you are innocent of the underlying crime, is that in the case that you are actually guilty and you get off because of the obstruction, then you are rewarded for bad behavior. It was extremely weird that he didn't want to get to the bottom of Russian interference in the election and was only concerned with the investigation into his roll. That is not how innocent people act.
No, he fired comey and shit, but it turned out he was innocent (of colluding with Russia).
He obstructed justice for a crime that didnt happen because he is stupid and those are his instincts.
He's guilty of something. Hence the 180 on the whole "yeah sure....make the report public." His taxes and that report hold A LOT of evidence.
He owes them. And it shows in how he acts towards Russia/Putin. The proof on paper would be the nail in the coffin. How his die hard supporters don't see it or care is baffling.
As a businessman I am sure (or at least don't care) what he did is totally legal. As a President.....nope. This is not good. He's in bed with them as a business person AND OWES THEM... and that can't be undone as President. In fact it's frightening.