According to internet think pieces, it's the lack of friction from space age law enforcement polyester clothing. It's designed for children, and can ben dangerous for adults. No word on what he was doing up there, though.

My honest guess it was a “Hay guys check this out” running jump into the tube

There's a large hard curve in the slide which would cause the slider to lose most of whatever momentum they gained from jumping into the tube.

I think the low friction polyester explanation holds a lot more water.

But him being face down points to that curve getting taken too fast and flipping him over

Yep, you’re dumb