Easy. The show was kind of boring and should have been connected to Masked Rider. I could care less about the whole being an "abomination" so much as how MMPR by the same respects was an abomination of Zyuranger, Dairanger and Kakuranger. So let's please drop that cop out.
The real reason why Masked Rider did not catch on is not because of the quality [since MMPR was of questionable quality as well] but because there were no more series to adapt without going backwards.
-Lack of advertising and promotion of toys. The way how the show's toy-line was handled is a huge crux why the show bombed. If kids couldn't remember it , how could I? There was rarely any promotion that I forgot that it existed.
-The show was thoroughly unexciting. To me, it felt like the M.Night Shyamalan's take on Ryuki. It ripped off other shows like Power Rangers and didn't find a balance between Ryuki's Rider War and the one villain organization basis of the Showa period of Kamen Rider. Through being too serious and a lack of dynamism and humor, it did not do well at all to entice me from ditching it. The cliche alien conspiracy plot/ alien alternate world is thoroughly bland and at the last 12 episodes, essentially throws the entire of the story development for a plot that is disappointing to say the least. I ditched Revolution and others for similar reasons and for a first entry in a family oriented franchise, it stinks.
If it was on Cartoon Network or Nick, it would have done much better and allowed it to have much more exposure, regardless of the quality. For being the first entry, its flaws would have been forgiven and by now, and would have been in Kabuto. If on Nick....its too obvious but I'd rather it be on CN so Shada [Voice of Finn] could have been Kabuto.