I saw this film for the first time this weekend, and was mostly puzzled by it, including @JohnT ‘s question about the characters’ motivations for virtually all their actions. But coming after the Trump phenomenon of 2015-2020, it seemed to me a complete parable about cults, and their inexplicable appeal to the simple-minded. I saw the Joaquin Phoenix character, especially the mindless violence he vented onto his Master’s critics (with verbal disapproval but endless love from the Master) as perfect. Hoffman gave a fabulous performance as a charismatic conman who praises himself to the ceiling and who seems to be a sincere believer in the gibberish he spouts and who is weirdly idolized by his many followers. The absolute nonsense he jabbers about, the neo-Scientology jargon that he keeps improvising (his son telling Phoenix “he just makes it up as he goes along” was great), coupled with Hoffman’s conviction as he spouts it, is terrific.
The plot is nonsense, so trying to figure out stuff like why Hoffman and Phoenix are drawn to each other is a red herring. This was an attempt to explain the inexplicable by simply showing it on full display.