I don't know when exactly they fell out, but from what I recall, aside from the occasional shady comment, Cam became openly vitriolic and began calling him a grifter when David did the whole pillow company thing. I don't think David has ever publicly responded though. Kinda makes sense that they wouldn't stay friends. Cam has always been a brash, unfiltered, unapologetic Gen-Z Leftist who proudly wears his mental health struggles on his sleeve. Whereas David has built a carefully curated, media-friendly Liberal image, likely intending to run for office once day.