I know I’ve read something Carlos Martinez wrote that was pretty good at discussing the material reasons for the split, but for the life of me I can’t find it; maybe someone else knows what I’m talking about.

It didn’t come out of nowhere, but Khrushchev recalling Soviet advisors and tech transfers was a HUGE provocation. China had and still does highly value advancing their technological position. Reform and Opening Up was as much about advancing their tech capabilities as it was developing the productive forces. Also, there really was an ideological difference over the USSR seeking peaceful accommodation with the west (ironic given how China’s position in the 70s overshot the USSR’s stance on this by a good margin). That’s not the whole story, just a couple parts that I can recall.