First off, I don't think Futurama "lingered and perished" for four years.
The Fox Exec's always wanted to kill Futurama, ever since Matt Groening pitched the show (hence the crappy time slots and such), but the show decided to prove them wrong and make lots of money.
If Futurama had started this year, Fox would have axed it by now, when you consider how anti-sci-fi TV networks are at the moment (The cancellation of Firefly, and more recently Century City and Wonderfalls come to mind).
I think the main reason that futurama lasted as long as it did (and WILL return
) is the similarities between it and the simpsons, the popularity of that show gave futurama a chance. None of the show's producers wanted it to be linked (or seen as a spin-off of) the simpsons, but it always gets compared with the simpsons. The last time I saw Futurama on channel 4, Vernon Kay introduced the show with the line "remember the simpsons?". The media always makes comparisons, and Futurama comics are selling well in the UK due to the way they are marketed towards the simpson's comic readers.