The second offy seems to be precipitated by the rider's unusual riding style combined with 'marbles' on the road surface.
He was clearly enjoying himself but his style is one of 'exaggerating effect' rather than exercising good roadcraft. By that I mean his positioning prior to a bend is more often than not absolutely wrong, and then he compounds it by committing to the bend at the wrong point and he seems to 'yank' the bars exaggerating the requirement so he can achieve a more stylish lean.
Just before he loses it, he had plenty of time to observe the 'marbles' at which point he could have traded speed, instead he yanks the bars and the low friction condition delivered the coup de grace. I very much doubt tyre tread or the lack of it was decisive either way.
Loose gravel is worse than banana on the road, and i also noticed the front tire was worn too much. The rider didn't respond to this remark though. Well, maybe he also thought it was not a decisive factor in that particular situation. And that's probably right.
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