It's kind of fuzzy to me now, but as I recall, they were clamoring for Obama to release his birth certificate but were met with constant refusals to do so. Once that was finally done and people got a chance to actually see it, then the matter ended for the most part, other than the few remaining hardheads who claimed it was a forgery. That doesn't validate what the Republicans were doing, but it could have been stopped much sooner.
Politics is about questioning and attacking the opposition. One side will study the opposition and try to find weaknesses, vulnerabilities, character defects, etc. in order to use it to their advantage. I think it's happened to other candidates and presidents, too, although it might involve different issues. McCain wasn't attacked over his birth certificate, since his origins and family history were well-known. But he was attacked over allegations involving his time as a POW in Vietnam.
I'm not sure why college grades would become an issue, but don't presidents and other politicians/candidates generally offer that kind of information on their political resume?
Oh, yes, I'm well aware that racism is still around. It's local to my area too, and it's even worse in other areas of my state which has led to Arizona getting some kind of national reputation.
In some ways, at least as a country coming to terms with its racist past, we still seem to have some work to do. I think we've made great strides in reforming and trying to do the right thing, but there's been this veneer of falsity about it that seems difficult to overcome. A lot of people might play the game well and put on a good pretense, but then they get drunk or something and a whole bunch of racial expletives come out of their mouth. Or even liberals who are ostensibly "trying to be nice" might still come across as condescending without realizing it.