Having watched the video very carefully, I am pretty convinced that this was the crews fault! (always blame the crew....) I have watched it frame by frame and believe that the crew actually loses balance just before the rig comes down and that he isn't thrown because the rig is coming down. What I believe happens is that the crew was acting as a backstay and when his weight came off the mast, he stopped acting as a backstay, the rigging broke because it was suddenly subjected to more load and the rest just followed on. The crew needed to be lower and locked in.
It reminded me of the 1983 505 worlds where there was a 40 knot squall. the 6 leaders were round the top mark and had their kites up. 4 broke their masts, one capsized and one stayed upright, mast intact and that result effectively won them the worlds. the crew was Cam Lewis and on spotting the squall, he hooked on and trapezed with his feet on the thwart so that he was acting as a backstay. With his size and leverage, that was enough to save the rig, while Gary Knapp did a great job of steering. Best bit of seamanship I know of in a dinghy.