The acrobatic the guy does here is called an infinity tumbling, where the wing rotates around you on the pitch axis. This puts a lot of strain both on the lines (which are generally made of kevlar) and on the canopy fabric. This is why acro wings need to be checked and serviced regularly. The pilot here probably didn't take into account his glider was not in ideal condition before doing the acrobatic. But yeah, thankfully he flew with a reserve emergency parachute!