This goes back decades. When The Jungle Book animated movie was first released, they did so right after the copyright expired, so they wouldn't have to pay royalties, and also so Kipling's estate had no say in what they did with the characters.
Now they act like the own the story. (Much like Pooh). Yes, the company that has lobbied extensively for effectively eternal copyright only respects copyright when it is their interest.
Like I said, they are a bunch of cheapskates that will take advantage of every loophole. But this was a little beyond that. They were in essence making new law. Granted not for the first time. But they were maintaining that if a company was bought by another that all contracts made with the first company were void.
You invent widget, license widget to company, company reincorporates under new name, does not have to pay you a dime. They have the rights but no obligations.
So if Disney were to reincorporate as Mouse Enterprises Inc, they could keep all rights but would not need to pay anything to anybody.