Note, Mary is the #1 name until 1962 when it falls to second place. Then it begins to drop rapidly down the list, until it is completely gone by 1972.
And what was going on during that decade? Legalized sale of the birth control pill in North America, plus almost complete rejection of Humanae Vitae in 1968, the long-awaited encyclical by Pope Paul VI on contraception.
Reject the life issue and reject the faith. It's all downhill from there on.
Parallel to the abandonment of the name Mary is the decline in the number of children per family.
The facts speak for themselves.