Most people say that Fox didn't like Futurama in the first place, which might actually be true.
From what i know it got pushed around in its timeslots since it existed, hardly got any advertising, and mostly was replaced by football games whenever the timeslot was needed. From what I've heard it even got left out of Fox' late Family/comedy program, where the commercials said "Fun starts at 8", but Futurama was planned to air at 7.
After all, they only ordered 4 seasons and not more. Due to the endless chain of pushing it around in timeslots it even happened that they split the 4 seasons they odered into 5 they actually aired. The last episode premiere aired was on August 10th of 2003. It got "cancelled" about a year before that.
look into the search feature for cancelled and you will find these:
Search for "canc".
Welcome to PEEL SMIDSY,
enjoy your stay here. As you already stated it as been posted more than once already, you will find this thread colosed because of that fact soon, I believe. Please use the search function next time to prevent that.

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PS: That story is all that I remember from reading here, some PEELers may actually know how it really was