Whatever caused it, could cause it again -- WITHIN TRADITION. Just look at the SSPX.
If Catholics in the 50's could fall for it -- they had daily TLM at their local parishes within walking distance -- you better believe the Faithful at "Traditional Mass chapels" nationwide could fall for the same thing. They're not exempt.
We still have the world, the flesh, and the devil.
We still have the tendency to take the easier path.
We still have the desire to fit in, be mainstream, and not "stand out", be called names ("conspiracy theorist", "rebel", "schismatic", "radical").
We are still surrounded by "our separated brethren" I mean heretics. USA is still a Protestant-dominated country.
We are MORE of a slave to convenience, impatience, etc.
We are LESS educated than those in the 50's, with less common sense.