He forgot to actually curl it. Like someone else said, the weights are almost certainly not actually 500lbs. Even elite bodybuilders and strongmen in their prime don't come close to curling 500lbs, let alone an old man.

Looking at the video, if it was legitimate, it would be 585lbs (6 45lb plates on each side plus a 45lb bar), which is even less believable.

Those are... very fake weights. Or AI. But probably just fake weights.