Yeah my post went over your head, so I'll try a different route. Considering the average NBA career is 4.5 years, if he plays overseas for that amount of time he would have a career playing basketball...really even if it's a shorter amount of time but I digress. Secondly you are missing the part of about if you play for teams overseas they pay your taxes, room and board which (you seem like a smart guy and can figure out) is significantly more than someone graduating college college and getting a silly email job making the same amount.
Also, people with email jobs love hiring ex-athletes so it really is just another checkmark on his resume so really there is no downside for him here, unless he were to die(?) playing basketball.
The way you are thinking about this is a bit odd and you're dismissing the amount of players who were much worse who make a living in one of the many leagues around the world. If you were a D1 player who played significant minutes you can play overseas if you want, it'll just take work.