it is considered acceptable to re-ask that question on to a new Stack Exchange site if you feel that the answers you received from the earlier time do not meet your requirements or expectations.
This is a classic case of cross-posting. The questions might be worded differently, but "why was this [4-season] show cancelled" and "why did they not make a fifth season" are equivalent. There was no effort to tailor the question to this site specifically in order to differentiate it from the previous question, which might have made it acceptable to cross-post if the questions were sufficiently different.
Ordinarily in cross-posting cases, we close and delete one of the two questions. However, if the question has received answers on more than one site, then it's often worth migrating and merging in order to preserve good content. In this case, since the OP had posted on M&TV first and then reposted on SFF a few months later, I discussed with a M&TV mod and opted to keep their version as the "master", migrating our version over there to preserve all the answers in one place. This is standard practice for cross-posts with answers.
It's basically the same thing as we do when someone reposts the same question on the same site (close and delete the repost, merge to preserve content if applicable), only with the extra added step of migration as necessary.