Sonic while casually destroying the fabrics of spacetime with glitches and camhacks: How come I can't outrun Knuckles? Knuckles: Programming, son. It's my official way of being even faster than you.
It's a Tool-Assisted Speedrun (or TAS), which means that the game was played frame by frame with heavy use of savestates to produce a theoretically perfect run. But also Hyper Sonic is super overpowered.
Have you ever given thought to how you actually watched this video? And how you were able to watch it? Have a sit and think about it... Seriously. We're human, we push what's possible as hard as we can, we're the only animal that does.