The filming of Ruggs during the draft said it all about him. First, he wore a white bathrobe. Second, he didn't look too happy when he was drafted. Third, his brother noticably looked mad the Raiders picked him. His camp basically went viral for acting a fool. I remember thinking that those were some red flags. The fact even one person in his circle was noticably upset on camera that one team picked him said it all.
Obviously, the Raiders couldn't have predicted that after they drafted him. But they most likely didn't do their full diligence on looking into the player and his background.