No, you don't get it. As I mentioned, the chance of him not subbotting is beyond low, miracles don't happen.
So firstly, the amount of money he does make is low as fuck in comparison to what most think, as he has to pay 5 bucks for those subs, in return he gets a growing channel and popularity.
But what you don't take into account is that people like Ninja come and go. Over the years there have been like a hundred streamers that stream a new popular game, get famous and earn a ton, and then drop down. I'm talking about people that have been in the business and consistently earning that 500k ish a month for a long time, not just off subs but also off branding themselves properly.
Ninja will not stay this popular, next month his subs will either halve due to amazon prime accounts having already claimed their skins, or he's a confirmed sub botter as it's impossible for all his subs to be brand new accounts. Either way, his income is reduced drastically from there and the snowball effect stops immediately, meaning his popularity will go into a decline.