It doesn’t matter if it was a joke - it describes a real, actual conspiracy that did happen.
The thing that makes jokes funny is the presence of an element of truth, so whether it was a joke is completely irrelevant to the fact that it reveals they were aware they were part of a seditious cabal with a specific membership.
I hope these traitors wake up every morning vomiting blood from the incredibly painful ulcers they are suffering.
They thought the baton would be easily passed to Cruella DeHill and their crimes would be swept under the Persian rug.....