It was neither. Sacrosanctum Concilium was the culmination of decades of study and work by the Liturgical Movement. Dom Prosper Gueranger is seen as the father of that movement. As abbot of Solesmes, he started the movement that led to the Vatican Edition of the Roman Gradual being promulgated by Pius X in 1908. Pius X continued with major reforms to the Roman Office, moving it further away from from monastic tradition, recognizing that secular priests are not monks.
The movement picked up steam in the 1940s with the Pian Commission which led to the reforms of Holy Week and the Roman Breviary. In the 1940s, a lot of experimental work was also carried out by the monks of Sant’ Anselmo, which is also the Pontifical Atheneum for liturgy. Things like versus populum celebration were first tried out there in the 1940s.
The general norms established by Sacrosanctum Concilium are the culmination of that work. The subsequent commission leading to the 1970 Roman Missal and Liturgy of the Hours was the practical application of SC. While many unofficial experiments were tried, so too were serious scholarly trials. Those are what led to the New Mass.
Anything outside the new missal are simply unauthorized deviations.
Any serious study of the history of liturgical reform should make all this obvious. Note I’m speaking exclusively of liturgy here. I’ll leave the interpretation of the rest of the council to those more well versed in those aspects.