Ok,, ski 1 is the one coming in from the left and ski 2 is the one filming.
First, the "Rule of good seamanship" always applies no matter who is officially wrong. Which means, even if someone cuts in front of you, you can not run into that person JUST because they were legally wrong for doing so. That said, if you can not avoid them, that is when the "Rules of the Road" apply.
OK,, Ski 1 comes in from the left and in theory would see the port (red) side of the vessel to his right. This means that ski 1 has the responsibility to do what is needed to avoid any issues with the other vessel as well as not force vessel 2 to have to change his path.
Since neither of the vessels are restricted in the maneuverability, then all the rules equally apply.
Once ski 1 turns left, (though the better path is slow down and turn right and pass behind the other ski), there is plenty of space between the two skis. Fair or otherwise, this puts ski 2 in an "Overtaking" position, which means he now must do what is needed to ensure clear and safe passage. Yes, ski 1 does a stupid hairpin turn, but if ski 2 would have continued his turn to the left, this would allow for clear and safe passage.
So officially, ski 2 is forced to give way due to the actions of ski 1. In the big picture, ski 1 did a careless act and should not have done so, but once he was the lead vessel, this forces any vessel behind him to be the responsible part.
This one is a bit strange as the "Rules" dictate fault. I was part of a situation as an investigator in a case identical to this. It had to be written up as noted above from a legal standpoint. However, ski 2 took ski 1 to court and ski 1 was forced to accept all responsibility due to "Reckless operation".
As the on scene legal force, we did not have nor could we use the filmed event. So,, for us it was a legal thing and pretty clear cut.
If the first ski would have passed behind the first ski, this would never have happened.
