Yeah I don't think most people realize just how difficult it would be to turn down a guaranteed 1 million dollars at age 16, like you don't just stumble on those opportunities.
Yes, he could likely have waited a few years and been set for life anyway - but what if the worst possible thing happens like injury and his career is over, its not impossible hockey is a very rough game. Then you have to live with knowing you could have set your family up financially for years and you didn't...extremely tough to swallow. Now, having signed the deal, "worst" case scenario is that he earns 1 million in his hockey career, even if he never makes the NHL or signs another pro contract in his life. That's a lifetime earnings for a lot of people at age 16, and if your family isn't wealthy its a life-changing amount of money.
I think the risk analysis was on point, so what you need to wait a few years to play in the NHL? Its a lot better than knowing there is literally no chance you don't get a bag and help your family out. If he passes on that, the chance is always there, no matter how small, that he never earns anything close to that again.