Pageanteers were way shorter (in height) back then
Today, being crowned Miss Universe often means that you will have to be rather tall. Most of the women who have a shot today tower at around 5’9, while weights remained far below the average weight of a typical woman at around 115 pounds.
During the 1970s, things were a little bit more forgiving. While slender builds remained a must, women who entered this contest were allowed to be a bit shorter. This decade saw the average height of a pageant contestant hover around 5’6.