To expand on meself's mother's eloquent observation:

I believe that my American generation's war, in Vietnam, developed the way it did because of the previous generation's experience. Those folks, as adults, had only experienced warefare as a tremendous shared sacrifice, one that everyone agreed was unavoidable and for the greatest of good causes.

It was difficult, if not impossible, for members of the "greatest generation" to imagine that any military action proposed by their government could possible be wrong.

Now, there were exceptions. General-turned-President Eisenhower, for one, seemed to have a pretty good idea of the situation that was developing at the end of 1950s when he coined the term "military-industrial complex" in his farewell speech. I'm sure that his unique position during WWII gave him an ultra-realistic perspective, and the ability to be more skeptical than most about the motivation of corporations in the armament business.