I mean.. if Netflix offered Disney more money then they wouldn't have felt it necessary to launch their own service. I think they simply underpayed or overplayed their cards. It's hard to imagine Disney with it's own service is getting the same amount of people viewing its content.

Having the services fractured just ends up with everyone making less money. Both the streaming services and the IP holders

Its possible Disney just completely overestimates how much they can make on their own - but market forces should correct for that eventually. We aren't privy to the accounting that went in to the decisions. They currently are making some amount of money off of their streaming service. If Netflix could offer substantially more than that amount (and more customers this way), then I don't see why they wouldn't shut it down