How exactly did America’s debt to GDP ratio decline so rapidly after WWII until 1980 given all of the generous social spending?

This is a FRED graph of federal debt to GDP over time, and it appears to have precipitously declined from 1945 to around 1980, despite large social spending by the government (Great Society, War on Poverty, Vietnam War, etc)

Was this because America's economy was growing so fast that it outpaced federal spending?