I’d not heard of him. I suppose decadent rich was not his to be, while the two or three biographical articles I’ve linked seem to explain. He was politically blacklisted, and rather than revert to suicide (a la Larry Parks), he went into film/book European writing exile. The surname “Knox” is apparently showbiz-crapola, because he was (apparently) of Russian-Jewish background.
His story might be even more interesting if his (apparently) unknown/out-of-wedlo<!–ck parents had been famous names. His reported friends Norman Mailer Gore Vidal were complex, profound, entertaining writers too.