Unfortunately, it became their business once a revolution came from the top-down. Priests trying to defend their flocks is precisely why the sedevacantist thesis arose as an answer as to why heresy and error were coming out of the Vatican. It became the business of the bishop, priest and layman once the hierarchy apostatized from the traditional Catholic faith. This is true also of the R&R camp of Catholics, and is why a traditionalist "movement" exists at all.
Fr's point was simply that the Traditionalist movement is the necessary
and end point of our reaction to V2. He would say it is an over-reaction to classify oneself as a "sedevacantist" because being a "traditionalist" is enough. If he were alive today, he would also chastise the new-sspx for their hopium mindset of "saving the church" and attempting to "make a deal" with new-rome.
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Fr Wathen's mindset was always "Do what you can (stick with Tradition). Don't do more than this (don't go into extremes and let the devil divide Tradition). Try to work together." For the most part, in the 70s and 80s, Trads did work together. But then camps were created, unfortunately.