Ideology is merely the surface, If you can go back a little bit, you can see Chinese intervention in Korea can be dated back to 600AD of Tang dynasty, no matter how many Empire may have comes and goes, Korea remains one of the core national interest of China.
As for the living standard and their government, no one can play god and tells the future but one thing is for sure, Ideology is not the key factor but money, DRPK had upper hand over SK until the 1980S and later ofc the fall of Soviet Union makes thing much worse.
SK raised during the reign of military dictatorship and their first pot of gold was rewarded by Americans for their blood
spilled over the Vietnam war which the SK general deployed 320K soldiers.