obviously counterfactual argument here but:
NBA has one and done rule currently which means talented high schoolers are waiting 1 year, typically playing in college or abroad, before entering the draft.
why not make some money alongside your 1 glide year by playing in the wyoming league? you get to stay in the US, boosting your future earnings, have some fun in college, but also earning some cash off of jersey sales and maybe lock in some sponsorship deals with apparel/shoe companies earlier than your competitors.
once one successful person does it, it's easy to see how it morphs into a market for eager one and done players.