China was friendly with the USSR only briefly, like in the 1950s. It was desperately poor at the time, and received a lot of aid from the USSR.
I don't know what other friendlies you mean. USSR installed communist/socialist governments in the countries it liberated from German occupation after WW2, but those relationships were... complicated.
Growing from a bad start and where you can copy a more developed nation makes this easier.
https://bearkunin.medium.com/soviet-union-facts-and-fictions...