The unpopularity of One Piece in the US also goes back to the manga scanlations. Back when there were only a few good fan translators, the one for the biggest group (Toriyama World?) loudly expressed his disdain for One Piece and refused to translate it, opting for Naruto and later Bleach instead. Thus, all of the early One Piece scanlations were done by bad groups. It also took until Kaizoku Fansubs to come along for One Piece to get decent subs while groups were falling over themselves to translate Naruto and Bleach, and we still ended up getting "nakama" out of that deal. One Piece got the short end of the stick in the US well before 4Kids got to it.
You are REALLY overestimating the relevance of fan translations to the popularity of these franchises with the casual anime fan. Fan translation are not what got Bleach and Naruto and whatever into Hot Topic, etc. Aesthetics, subject matter, music, etc. matter way more. Bleach is "cool", Naruto has ninjas - you don't have to look much deeper.