Why was the government of Ngo Dinh Diem unpopular?

Diem was a US puppet. Corrupt and quite unpopular with ARVN troops. He stole US aid money and denied the populace the supplies we sent them, choosing the blackmarket instead. He considered himself a strategic asset and a tactical genius. Everybody considered him unreliable, even we US soldiers lower than general strategic rank. One of the reasons we lost the war and they lost their country in a civil war in which we should have never intervened.