That's oversimplifying, but it was certainly a big part of it. People are incredibly self-centered...so much so that they don't even notice it. If something isn't affecting them or people that they know directly, most people will just ignore it.
Please note: This is not a criticism of the anti-war movement in the Vietnam era. It was a totally stupid war for no reason that was ever explained ... or rather the explanations did not justify it, and were often lies. The ani-war movement was just, moral, and proper. It also woudn't have happened if people who had access to power weren't forced to face what the war might mean to them.
Please note, the current wars in the middle east are much more justifiable, though nobody in government dares to mention the real justification: oil. The wars are a blatant resource grab. (I'm not sure this extends to Afghanistan. I think that may be basically a war to test out the new military toys in a live exercise. But I'm not sure.)
Please also note that the "military toys" currently being developed and debugged are designed to allow a government to attack an armed civilian uprising. And note that simple verstions are being distributed to various police forces all over the US. This may explain what the real purpose of that "war" is.