Here's the way I see this incident. I accept that accidents happen. However, more accidents happen when people are negligent or incompetent. This was the final of a PWA elimination. Taty's behaviour should be measured against a very high standard - one of the top 8 slalom sailors in the world. When I read his excuse for this accident, it suggests to me that he did not display the professionalism expected of someone at this level. He says he did not see Pierre but have a look at the video.
windsurfing.tv/video/worst-slalom-crash-ever-taty-frans/
You will see that Antoine Questel was in fact between Taty and Pierre. Questel spotted Taty on his cruise missile trajectory and had to slam on brakes, go downwind and eventually jump off his board to avoid a crash. Then it's worth noting that Pierre's board (which is basically level with Taty's) actually touches Albeau's hip.

If Pierre hadn't been in the way, Taty would probably have hit Albeau and even with Pierre as Taty's buffer, Albeau nearly copped it too.
So Taty seems to have lost sight not only of Pierre but of half of the field he was racing against. By the high standard that Taty should be measured against, that is incompetence. But it doesn't end there. Taty decides to blast off downwind just before the mark without looking around to see where everyone is. That is reckless. Taty's sailing was unbecoming of someone competing at this level of the sport both in terms of skill and awareness.
Accidents do happen so the real issue here is that Taty's response is not what I expected from the man. When you have clearly stuffed up majorly, it is incumbent on you to take full responsibility for the accident. That means a genuine and personal apology. Let's just remind ourselves what happened here. This image shows just how close Pierre came to getting a fin through his kidneys, spleen, liver, lungs or spinal chord.

How does Taty respond to the fact that his mistake has injured Pierre, affected Pierre's event chances and could have killed Pierre? He says he sent Pierre a direct message on Instagram!!! Even for a millennial that is outrageous. Instagram?! The least Taty could have done is call Pierre - as soon as possible after the accident. It doesn't matter what people told him about Pierre's condition; it was up to Taty to find out from the horse's mouth. And if you read Taty's Facebook post, he still hasn't apologised. He spends the whole post justifying what happened.