I think you are misinterpreting "most faithful", giving it too extreme a meaning. There are those who have a mild interest in Medjugorje; there are those who visited and were interested for a while, but less so now. Then there are those who follow the messages frequently; these fit the phrase "most faithful", as long as we don't exaggerate its meaning.
Many, but not all, of this latter group will fall away, as I explained. The official disapproval of the Church will weigh heavily on many Medjugorje supporters, and the confusion of the great apostasy will make matters worse.
Roman Catholic theologian