I think this is a question about what is legal based on the letter of the law and what is right morally. History is riddled with people/corporations profiting off of unpaid or underpaid labor which might have been considered legal at the time but was clearly not ethical or moral. Technically, the contract Chapelle signed in the beginning didn't give him the ability to earn money from its current streaming. Whether that's because he didn't have the clout then or streaming wasn't a thing, it basically means a corporation is earning money off of something he created, wrote and performed in. A show that almost broke him.
Sure that's legal. It's "business." But so is approaching Netflix about removing the old show from their service. They pay him a lot. They value him. He has the clout now to make demands. If I'm Netflix, do I risk my future relationship with him just to run a show that is available elsewhere but that makes him unhappy knowing other streaming services would line up to not only pay him but also not air a previous show? Heck no.
I'm not a fan of Chapelle but it sounds like he can't win if the restrictions of his previous contract are just tough luck and using his current popularity to negotiate things he wants is an overreaction.