For years, the Catholic Church, guardian of the entire Truth, fought against "the world" and "the prince of this world", Satan.
At Vatican II, due to the influence of Modernism (condemned by Pope St. Pius X), many bishops desired a "truce" with the world -- they wanted to be accepted at long last. They were sick of being looked down on by "men of the world".
Vatican II was for the Church was 1789 (the French Revolution) was for Europe. The latter was the death-knell, the nail in the coffin for Christendom (=the Gospel message having worked its way into the social fabric of life). The former was the surrender of the Church to the world FORMED BY that revolution -- a world that had completely cast God aside.
That will have to do for now -- on this issue, I could write a book.
In Christ,
Matthew