One day in the center of the Earth, the almighty Sam Raimi decided to assemble some hidden cameras in order to record the ass kickery of a Bruce Campbell weekend. The show was deemed unsuitable for television, due to the fact it would literally destroy all other television shows.
Since a Television program would be unsuitable, it was planned to edit all three planned seasons into a trifecta of orgasmic action. The films were released with years in between, so audiences could absorb the films one by one. If they were all released at the same time, the Earth would've imploded on itself.