At 16 it's normal for him to see other people making money online and think it's easy, but the thing is, making such a big decision based on 6 months of obsession... that's risky. I know people who got into this and most of them realize after a year or two that it doesn't make the same money they imagined, or that the content they create doesn't interest them anymore. The algorithm changes, the competition is brutal, and without finishing basic education he'll regret it later.
What works better is not making it "all or nothing." If he's really drawn to streaming, let him do it after school, on weekends, during times that don't interfere with school. Then you see if he can keep up with the consistency or if it's just a fantasy. Most of the guys I know who tried to live off this at that age ended up going to classes anyway because they needed money urgently and didn't have any backup. Plus, even though it seems boring, finishing high school opens doors you don't know you'll need 🤷♀️ if he really does well with streaming in a year or two, he can always focus more on that later; but if he drops everything now and it doesn't work out, catching up on those years of study is complicated.
My suggestion: talk to him without judging, set a clear agreement (schedules, minimum grades, household chores), and let him explore while keeping what matters. If at 17, 18 he's still just as dedicated and seeing real results, then you can reconsider. But at 16, dropping everything is premature.