Delusions about winning wars with only air power are very close to a century old now. ( https://en.wikipedia.org/wiki/Bomber_Mafia ) But they seem hugely appealing to parts of human psychology - so "proved horribly wrong, yet again" doesn't do much to cure them.
That said - Gen. Clark was a career Army officer, not Air Force. And "we don't need an army to win" ideas have, ah, limited appeal to career Army folks. My read is that he was a good officer, stuck under a political leader (Pres. Bill Clinton) extremely reluctant to commit ground forces. Clark knew not to contradict his boss, and did what he could within the imposed constraints.
