stupid (understated) political decision for China. Actually a pretty Machiavelli geopolitical/ inner political decision for China:

The sino-soviet split basically created an atmosphere where both countries comes to support opposite sides throughout conflicts from the split to the collapse of the Ussr (Angola, Afghanistan, Ethiopia-Eritrea, etc.). The outcome of the war is pretty vague, Chinese people would tell you that they are close to reach/bomb Hanoi but didn't because that would escalate the conflict while I believe that it was an ill prepared operation to begin with. Regardless of the judgement of the outcome there are 2 things that happened:

• it shows to the world the incompetency of the USSR to support its allies in the time of war, reshuffling the future geopolitical alliance to come.

-the Incompetency of the Chinese Military brass to adapt to modern warfare allowed Deng to reform the military / Purge the military (theorize on how it helps with the cementation of Deng's power within the politburo)

Either way, big socialist bros fighting, little brothers get hurt