If you think this, you may not fully grasp the scope of Disney's plans. They did not want to be left behind in the streaming era. So they went all in on "Direct-to-Consumer" as their main business. De-emphasizing theatrical/box office and broadcast; competing with (beating) Netflix, NBCUniversal, and all the rest. Not only in the U.S., but globally.
There was NO way they could do that with just their existing catalog. They did not want to be a niche $5/mo. add-on platform or a channel on jointly-owned Hulu, which is all their existing content would have got them.
So they bought a bunch of stuff and started cranking out a bunch of stuff.
BTW, this is relevant to people here: the stuff they bought and cranked out was--on purpose--not more of the same type of stuff they already had (and that many here might prefer). It was to deliberately broaden their audience. Disney fans were already going to subscribe to D+/Hulu+. They needed to be able to offer content that appealed beyond the base.