I don't think scientology or Hubbard "went wrong" at all.
In my opinion, scientology does exactly what Hubbard intended it to do:
it brought power and wealth to Hubbard.
He created a "game" that was intended and designed to get people to "flow power" to him in the form of adulation, energy, money. They did. They still do.
Whether or not along the way anyone got better or had their life improved, or their life ruined, is irrelevant to the actual purpose of scientology. There are people who swear that scientology saved them. There are others who testify that it ruined them.
Regardless, Hubbard got what HE wanted and that's what it was all about -- it really had little or nothing to do with YOU, the pawns (the "pieces" as he called them) of the game.