Executive Meddling/Old Shame: According to this interview with Danny Wells, Nintendo was reluctant to do Super Show from the start and had to be cajoled by DiC to make it work. Nintendo finally agreed to license the series but wanted no more after production for its lone season ended. This may also explain why there have been no Western Animation adaptations of Super Mario Bros. since 1991. (The Saturday Morning Show Super Mario World and Captain N lasted a couple of years longer, regardless.)
As this link states, the poorly-received 1990-91 Re ToolClub Mario disappeared into a black hole after it was taken off the air, and there are longstanding rumors that the master tapes were trashed. However, the Club Mario version of the episode "The Unzappables" is the one that's on iTunes and Amazon instead of the original version. Some attempts have been made to Keep Circulating the Tapes though.