I don't see would-be evangelists as "preying on loneliness" so much as offering (from their point of view at least) a potential source of relief from it. - Knowing your market?

When I was quite young, my widowed mother was searching for something in life, and joined the JWs. I only remember two things, one was their venue, and the other was their US preacher had come over for 3 months and we housed them, free of charge. Then my mother went into hospital for an operation, a benign growth I think. Anyway she had many visitors, and even an old school friend who she had not seen for 20 years. No JWs. End of story immediately.

I re-enforce (sic) the cynical but experiential "preying".
And their rules and methods are legion. THEY are not benign. Pyramid selling is as close a description as I can come up with because money hierarchy are key motifs.