toughpigs.com
>The role of Kermit the Frog is an iconic one that is beloved by fans and we take our responsibility to protect the integrity of that character very seriously. We raised concerns about Steve’s repeated unacceptable business conduct over a period of many years and he consistently failed to address the feedback. The decision to part ways was a difficult one which was made in consultation with the Henson family and has their full support.
As well as the reasons why he was fired:
hollywoodreporter.com
>In a Monday interview with The Hollywood Reporter, Whitmire explained that he was let go by Disney in October. He was given two reasons: unwanted notes during the short-lived Muppets reboot on ABC and a union disagreement. News of his termination has since come to light after months of being told he was going to be "honored for his contributions" to the Muppets and the hope of working out issues with Disney brass.