Only the 'big' franchises from Japan were being played in Europe. Final Fantasy, DQ 8, a little bit of SO but other than that a lot of series or stand-alone games didn't even make it to Europe. Xenogears, Arc the lad...
My guess is SMT wasn't known for being a 'good' series out here somewhere until the release of P3FES.
Maybe the world wide web helped a bit for SMT.
Digital Devil Saga and Nocturne (Lucifer's call) did some of the ground work during Ps2's reign to build the SMT name. Maybe that helped P3fes to sell a bit more than usual.
Although these numbers are not to be trusted of course...







