There are many people who climb Everest (29,032’) without supplemental oxygen. Also, he’s not expending any energy (except trying to keep warm) so while I wouldn’t want to try it, its possible to survive, in that regard
Maybe also prepared extremely heavy clothing? One might assume a lot of preparation, but it is Kenya, and he is an illegal immigrant, after all - so I doubt it.
Probably just a very lucky criminal.
But the climbers get to a base camp to allow themselves to adjust for the altitude, seems like for a pretty long period of time before they can make that final ascent. Just seems crazy to me, I’ve been to the altitude chamber and I know what hypoxia can do to a person. Also, I happen to fly the 747 and it just boggles my mind that he figured out how to ride the gear as it was being retracted without being squished .