Earlier quoted context omitted.
Disney was founded on Mickey Mouse. Yes, they made major motion pictures out of old myths and legends, like Cinderella and Robin Hood, but those stories have always been public domain and you can write a book or movie about them with no problem.
Not sure about their finances back then, but I have to guess that their feature films were the money makers and the shorts less so. And I think the grandparent's point is that Mickey Mouse today is in some sense analogous to your Cinderellas and Robin Hoods in the 30s... only you can't make your own movie about him.
Their first feature film was very profitable, but it was from about 15 years later (https://en.wikipedia.org/wiki/Snow_White_and_the_Seven_Dwarf...).
However, their next two movies (Pinocchio, Fantasia) cost them money because they were released during World War Two, when they couldn’t show them in large parts of the world.
They needed Dumbo to make up for that (https://en.wikipedia.org/wiki/Dumbo#Box_office), then Bambi wasn’t a huge success, either (https://en.wikipedia.org/wiki/Bambi#Box_office)
So, I guess it wasn’t till after World War Two that their feature films became profitable. They survived, so chances are the shorts brought in money.