In Luther’s time, Christianity was at the center of culture because of the power and social, political position of the Catholic Church; this had been going on for centuries, at least since the Middle Ages. The traditions of the Church saturated everyday life on every level. It could never have occurred to Luther that there would be a society that would not know the Church Fathers, the sacraments, Christian creed, doctrine and teaching.
Luther’s concern, in part, and I think it was legitimate, was the imposition of man-made ritual, practices, philosophy, onto the fundamentals of the faith, more man than God driving the Church. There was a loss of balance, perspective, in much of the Church, corruption, etc; also the laity were quite estranged from the Church ecclesiastical structure, practice.
Luther wanted to reform, reorient, simplify the practice of the faith, back to its original roots. The idea of Sola Scriptura reflects this desire, but is in error, I think. It is too radical and ultimately makes no sense, as the Church put the Bible together and interpreted Scripture from the days of the Apostles.