Tree wells are absolutely terrifying. That dude just won the life lottery there, as they were not skiing together, and the skier just happened to be on the same line that the buried boarder was on. Nationally, tree wells kill as many people as avalanches. Luckily, the US has a very good record on avalanche deaths, when compared to the rest of the world, where avalanches occur.
According to one interview of the dude that did the rescuing, that boarder was even prepared with his own back country kit and was skiing with 3 other people equipped with avalanche transceivers/beacons. None of his group saw him go down.
From Oregon in 2019, three people died in wells in as many weeks:
Here is an old video of a skier in a ski patrol group going down a well to show how easy it is to lose someone, if your not paying attention: