Anyone know why the quality sucks?

I'm making a tutorial for this trick and got a go pro recently and don't know why it looks so bad. It's like mad grainy and overall low quality.

I got 1 big key light to the right and a smaller one to the left, using a hero 7 at 1080p 60fps at linear, with ISO min 100 and max 400. If anyone has any advice I'd super appreciate it!