Just think of how widespread Modernism was at the time of Vatican II. St. Pius X had all he could do to root them out with the Sodalitium but by the time of Vatican II (after Benedict XV, Pius XI, and Pius XII rolled back the effort and let their guard down), the Church had become absolutely infested. St. Pius X said that even in his day, with all his efforts, that humanly speaking the Church was finished. Father Feeney at one point wrote to all the bishops of the world about needing to reaffirm EENS dogma (had nothing to do with BoD at the time), and he received only 4 positive responses. 99% of the American clergy were absolutely infested, between accepting evolution, the Big Bang, denying the inerrancy of Sacred Scripture, religious indifferentism, pretty much the entire Syllabus of Errors, etc.
That's why God took the Noah and the Sodom & Gomorrah approach, let the Conciliar Church take over, and then told His remnant faithful: "Go out from her, my people; that you be not partakers of her sins, and that you receive not of her plagues." (Revelation 18:4). He instructed His faithful to get out of the Conciliar Church. So He chose to separate the wheat from the chaff, the weeds from the crops, by doing it in reverse, by pulling the good out so that the bad can be burned. Just as He put Noah and his family on the ark and then proceeded to flood the entire world, and told Lot and his family to leave and then proceeded to incinerate Sodom and Gomorrah, so He's had Traditional Catholics leave the Conciliar Church ... so that He can wipe it out.