The main reason why the public became informed of the horrors of Vietnam was because this war came at a time when media coverage was unprecedentedly powerful. The war, which ended in 1975, came at a time when TV was common in every household. People followed news of the war in this way, and they were able to learn a lot more about the details of the war than they would have been able to do in the past (when most news came through the newspaper and letters from soldiers).
Moreover, not only were people able to follow the news on TV, but they were also exposed to images of the battlefield. The devastation and suffering shocked the public, and increased opposition against the war.