What is the significance of the key songs and key scenes in the movie Good Morning, Vietnam? Why were they chosen?

Good Morning, Vietnam is a 1987 movie in which Robin Williams plays Armed Forces Radio Service DJ Adrian Cronauer in Saigon, Vietnam in 1965. Key scenes involve Williams's improvised on-air monologues in which his character, Cronauer, criticizes the war in Vietnam and the way in which the American politicians were conducting it.

Many of the scenes involve the music that Cronauer plays for the American troops, and the lyrics of the songs have particular meaning when they are played over scenes of troops in Vietnam. For example, he plays "Nowhere to Run" by Martha and the Vandellas when showing pictures of the troops in Vietnam. In one scene, he dedicates Louis Armstrong's "What a Wonderful World" to troops he has met who are traveling through Vietnam, and, as the song is playing, there are scenes of troop movements, Vietnamese people sleeping on the ground, Vietnamese people washing clothes and themselves in dirty rivers, and Vietnamese people getting bombed from the air. Later shots include a lone bloodied sandal in the street, Vietnamese people being marched at gun point by American soldiers, and a street demonstration in which Vietnamese people are hurt. The song is of course ironic in its intent, as Vietnam during the war is very far from being a wonderful world. These songs were chosen to reflect the time period of the Vietnam War and to offer ironic commentary on the senseless way in which the war in Vietnam was being  conducted.