Oh, really?
Why?
Why would any FSSP priest " just leave"?
Oh, no big deal.
He just woke up one day and decided to go from
* A large organization with structure, resources, benefits, etc. to a rinky-dink organization with none of those things
* An organization approved by Rome to a group that isn't even accepted by most Traditional Catholics
* A respected world-wide organization to a scandal-ridden de-facto cult that works with a superstitious lay exorcist, a con artist, and several priests with tainted reputations (the sin that dare not speak its name)
* A group with standard seminaries and training to a group whose "seminary" involves no formal subjects or classes. I'm not making this up: in Boston, KY, the "seminarians" are told that each of Fr. Pfeiffer's rambling, disorganized, 2-hour rants is supposed to be the equivalent of several classes of Moral Theology, Canon Law, Dogmatic Theology, Ascetical and Mystical Theology, Scripture, Logic, Philosophy, etc. (And you wonder why Bp. Williamson and the other Resistance bishops refuse orders to these "seminarians")