When you come down from the mountain, you have to "hit the brakes" at some point, and find a new level of spirituality you can maintain as a layman in the world.
I've heard about ex-seminarians falling all the way down to losing the Faith after their seminary experience. I always wondered incredulously about that -- until I read this. This level of disillusionment would do it.
Remember, these men have already given up on "Novus Ordo land", and consider that THIS is the anti-Modernist resistance (pardon the term -- I'm applying it to the SSPX in this case), where the good guys are. Once you are forced to give up on those "good guys", then what? Where does that leave you?
It's very dangerous for a young, idealistic man to come face-to-face with the Church's frail human element. It is always a Faith-testing experience. How each man fares depends on many factors.