Niven appears to have been in on the discussion but not "at a science fiction convention." They lived in Pasadena or nearby one another, and were acquainted. In general Hubbard was known as a blowhard and a marginal writer. A bet? Perhaps, but it wasn't the *result* of a bet. Hubbard wanted to make money and escape taxation. During that period, several others did create "churches" along various themes, mostly vaguely Eastern woo. The Internal Revenue Service (IRS) was very skeptical and indeed attacked the Scientologists. For this reason, Hubbard bought a large boat, intending to escape extradition by remaining on the high seas. He finally got very ill and lived in hiding in Clearwater Florida for the remainder of his days, scuttling crabwise from house to house through hidden passages if the story is true. Clearwater is a bit like Utah in that speaking ill of the religion makes you persona non grata. Scientology is a family enterprise, a business if you will.