just like vietnam, the two regimes were natural enemies. even if north didn't attack, skirmishes would have happened everyday and eventually lead to war. it would be the same for every nation, always cvil war happens.

two exceptions:

germany. simply because too much importance to both america and soviet, and each wouldn't hesitate to go nuclear if needed, this resulted in absoultely no independent sayings from the two germanys.

china. TW is an island, with backing from america, PLA had no power to take it. and soviet couldn't really help ccp on this.