Start with Lyndon Johnson's need to win a second term. If Vietnam fell to the communists before the 1968 election, LBJ knew he would loose.
Gerald Ford was more a victim of the TV coverage of Saigon falling to the North Vietnamese communist, in 1975, then he was a victim of his Nixon pardon and the intellect (?) of Jimmy Carter. A president who is in office when a war is lost, will not be reelected. Johnson knew that in his bones.
The healing will start when the Democrats own up to their complicity in escalating Vietnam for domestic political reasons and not for national security
Some things never change. Seems everything they do is for domestic political POWER and NOT for national security.
Most wounds don't heal when you keep picking at them; they get infected.