Archbishop Lefevbre never wanted, and stated it, a bishop to lead the SSPX. He wanted a priest to do it. That's why before Fellay became Superior General, Fr. Schmidtburger was the SG. I have no idea how he finagled his way to that position, but the reason the Archbishop didn't want a bishop there, was so that people would not be confused by a false aura of authority coming from the bishop.