We don't knowquestion: how exactly does Gamefreak decide which Pokemon to heavily market? Like, for example, Lucario from Gen IV onward
They probably just test the waters with various Pokemon they think will be a hit (Lucario, Zoroark, etc) and if its successful (Lucario) they market it more.
Things like the starters or box legends get heavy marketning because they're the face of the generation that you can't NOT know about or encounter in the games.
Pikaclones get relatively heavy marketing probably because they're pikaclones
Oddballs, like Stunfisk, probably only get a marketing push when they see it's well-liked.