Monster Hunter was on PS first wasn't it? Plus with the huge install base of the PS4 and brand strength of MH it's likely to do well.
Monster Hunter's sales didn't explode until going to portables though, and Monster Hunter Tri, which came after that explosion, although selling better than the previous console games, still didn't approach the portable ones at all. Now, the sales hadn't grown for a while, which is probably what led them to making MHW for a different userbase, but this big growth will have to come from Western markets and it will have to make up for inevitable sales drop they'll have in Japan.
I'm actually still surprised elements like the monster's (lack of) hitstun (outside of specific conditions) and most movesets seemed to remain similar to the previous titles - basically the core of the gamplay is still there. If they're really intending to court a more "mainstream" western audience you'd think they'd go with more standard controls and damage system, but in spite of streamlining other aspects, the core of the gameplay is still the same Monster Hunter that often seems to be met with criticism outside of its established audience.
I guess they hope presentation and "home console" will allow them to reach a largely untapped market in the west that haven't even tried the games yet, making the franchise blow up in the West, without changing its core, but that's a very risky bet.