Actually South Vietnam was practically given to the communist north on a silver platter after Nixon was forced to resign over the Watergate scandal and Gerald Ford resumed the presidency...It was in 1975 Saigon finally fell and was re-named "Ho Chi Menh City".
The Vietnam War was really unpopular by then...My speculation is because Gerald Ford was going to run in the 1976 presidential election against Jimmy Carter (which he did), it would make a great political stunt on Ford's part to gain votes by being "the president to finally end the Vietnam War"...even if it meant giving it all to the communists. Of course, that's just a speculation on my part.
As it turned out, Carter won that election anyway.
Actually South Vietnam was practically given to the communist north on a silver platter after Nixon