If I had to guess, based on the little info we have and the (possible) blood in that video, I'd say that he flew out of the raft on that bump and then the raft kept going and he landed on the slide. So basically the mesh kept him from flying off the slide completely but it did little else for him if he was ejected from the raft.
All speculation, of course.
I am truly horrified by the whole thing. People assume rides are mostly safe in parks. And with no age restriction, I'm sure these parents thought the same. It's so sad. IF the ride ever reopens, I bet the age requirement will be 16 or maybe even 18.
I doubt this ride will ever reopen. Who would want to insure it?