I don't think it was necessarily fixed, but Cowboy has been destroyed in many of his last fights (more importantly, the last two, where he took massive damage). Not only does that mean that McGregor is not the first one to do defeat him, but it also means that Cerrone has taken tremendous damage, so each beating that he takes is worse than the last one.
Still, it is possible that it was fixed - I am not discounting that possibility and I understand why many people claim it was. For the people that say that Cerrone wouldn't take a dive... how do you know? Do you personally know him? You can't say for sure he IS or ISN'T the type to take a dive. None of you know him. He doesn't even know you exist, so stop acting like you are his buddy.
I repeat - I am not saying it was fixed or was not, but regardless of whether it happened, beating Cerrone at this point is nothing special. In fact, that's why I was never looking forward to this fight - it felt like going to the dollar story and purchasing Chinese knockoff sunglasses and being told that they were Raybans. The advertising was just so transparent for any MMA fan to see through the bravado (and by MMA fan, I mean anyone who doesn't tune in just when McGregor fights).