Archbishop Lefebvre lived at a certain time and place. In the late 1960’s – early 1970s in French-speaking Europe (and not only there, but that was his place), there was pretty much total disintegration occurring in seminaries and also in many other Catholic institutions. The Archbishop started a seminary (which became the SSPX) to take care of the problems in his place and time.
The SSPX ended up spreading all around the world due to the extreme measures that were taken by bishops and priests against those who wanted the Catholic mass the way they had always had it, and who wanted Catholic doctrine the way it had always been taught, and who were appalled by what was going on in the Church in the name of Vatican II.
These people begged their priests and bishops for help and were told that Catholic doctrine had changed and that the old mass was banned and was never ever coming back. Their children were taught heresy at Catholic schools and their pastors tossed out the statues and jackhammered the high altars.
These people begged the SSPX to come and help them, and the SSPX responded.