Sounds like his philosophy fit may have fit in with the broader prosperity gospel space, Napoleon Hill, Billy Graham, Norman Vincent Peale, et al. Potentially worth looking into. Also related to the self-help movements and the New Thought philosophies.
fascinating that he wrote a book Copywriting and Direct Marketing. This may also tie him into the theses of Kevin Phillips' American Theocracy?
Link to: https://hyp.is/E4I_qgvCEe2rQO9iXvaTgA/www.goodreads.com/author/show/257221.Robert_Collier