In an article after Jim Henson's death, which is evidenced by Frank Oz that it's Michael Eisner and Disney's fault. It says "After Henson's untimely death, his family had "second thoughts" about the merger, which then fell through. The Hensons even sued Disney for "continued use of the Muppets," accusing them of "outright theft of Jim Henson's legacy." Disney countersued, claiming that they had an oral contract with Henson. Even though things got uglier than a Skeksis butthole, the two sides eventually settled. Here's more information from the article. https://www.cracked.com/amp/article_27126_boy-disney-has-sure-screwed-up-muppets.html