Look no further than Hamed's record after the fight... Then actually watch the fight. Then throw yourself down the nearest flight of stairs for asking that question. It's actually both; he was exposed by having a very bad night.
It was neither. He looked really vulnerable in his fight before against Augie Sanchez, who was limited at best and had a meaningless career. He looked like crap against Calvo in his last fight. So he closed his career looking bad three consecutive times. It's hard to call that an exposure or an off night. But he looked great against Bungu in the fight before Sanchez. Bungu was coming off 13 consecutive title defenses. You're the real deal if you dominate and spark out a fighter like that.
We had already seen these flaws of Hamed numerous times, Barrera was just the one who was good enough to exploit those flaws enough to beat Hamed.
Bungu had a split decision win and a majority win at 122 just before moving to featherweight. He's the overrated type of fighter that Hamed's fans use to justify his overrated resume.
I hated Hamed. He was the real deal though. Athletic, natural, and had crushing power. Barrera beat him well and good, but Hamed still had a punchers chance and went the distance. Hamed was exposed and also vindicated by that bout. He was vastly overated in his time, but I think everyone knows it as you don't see him on VS threads. He had talent, but that only goes so far. He was in that fight, it was a solid win for Barrera but not as one sided as people make it.
Hamed had incredible talent and like most boxing prodigies success went to his head and if he was more dedicated greatness could have been achieved and Hamed was his own worst enemy.
Everyone knew what Hamed's flaws were just by watching him but you still had to be a special fighter like Barrera to have the ability to capitalise on those flaws.