Yes, he was basically warning that short termism, and constantly throwing people under the bus, will be bad for American imperialism in the long term.

"Word should be gotten to Nixon that if Thieu meets the same fate as Diem, the word will go out to the nations of the world that it may be dangerous to be America's enemy, but to be America's friend is fatal."

Thieu did meet the same fate, well, he wasn't killed, but he was overthrown and lived life in exile as a recluse.

Zelenskyy will almost certainly suffer the same fate.