This is troubling. What kind of FO, does do their homework and due diligence when making their draft choices, making sure, there are no skeletons in their closet.
I doubt there is super deep investigation done on most 4th/5th round picks.
1st round picks sure, because you only have to investigate 10-15 players who you may be considering at the spot you will be picking. And that's a very valuable resource that you don't want to end up wasting because you didn't know something. If you're talking into the 5th/6th round then you're investigating 200 players. How much can you investigate that many players besides just googling their name and seeing what comes up? And the value of a late round pick is much lower, the cost of investigating hundreds of players is probably more than the cost of a 5th round pick.
Why didn't the Bills stop playing him or release him when they found out in July is certainly troubling. I don't know if they should have known about this before then. Nobody else seemed to. I'm more concerned with why SDSU and other entities didn't make this more known than the Bills not having been able to uncover the story themselves at the time of the draft.