He's signing with Nike, and he's arguably way more profitable for Nike than most pro runners. His job is to present products and he has a lot of influence on HS kids, he can easily make them want to buy Nike stuff. While, honestly, no one on earth is going to buy a shoe just because some "B" pro runner wears it and says it's a good shoe.
Obviously he's not as profitable as Eliud or Jakob but he can still get a very good deal with Nike and make a decent living for a 19yo with his sponsorships, his Nike deal and his YouTube money.