They might as well have contemplated buying Reddit.
Imagine if it became a sanitized family friendly microblogging platform where it was all pure, clean, fun conversation, anything not sparkly clean got knocked off. That would have ensured its death and would have shrunk to maybe 10MM users total.
As a regular user of both platforms I see where you're coming from, but Twitter has more of a mainstream presence. There are politicians, brands, famous people, etc.
Maybe someone that might only hear about Twitter from the news (and not actually use it) could think it would be a good fit for Disney.