I think because of the blue skies and sunshine in the video, it all looks clear cut. Remember, he was in sinking air, probably with significant variations in the amount plus there was a bit of wind, I'd guess coming over the ridgeline he was trying to cross.
You often get a venturi effect over the top of a ridge, which intensifies the downdrafts on the lee side and also has the effect of locally increasing the wind speed, so a double-whammy if you're heading into it. I've had this happen to me when crossing mountain passes - everything looks OK then you're shot down at the last minute. Once it took me three goes to get over a particularly nasty one in the French Alps but I had several thousand feet of clear air to fall back into and try to climb up again - he didn't, so IMHO a wise decision.