In reading the histories of the various Russian True Orthodox Catacomb Churches formed under the communists, Matthewites, the Synod of Milan, and the GOC-K, I have begun to realize why there is a division.
Under communism, catacomb Orthodox Christian bishop were often secretly ordained. They simply could not have open consecrations. Sometimes records were kept, but sometimes no records were kept in fear that the Soviet spies or freemasons would retaliate or go in search of these newly consecrated bishops and their consecrators. Those records that were kept were often destroyed as communists bombed and destroyed churches or places of residence. Records were also buried to preserve them, but then construction by the communists often destroyed these hiding places.
When the Iron Curtain fell, these True Orthodox were still worshiping in secret since they were not under the politically correct Moscow Patriarchate (MP). When they obtained permits to build churches and tried to operate in public, their vestments, liturgical books, relics and churches were often seized by the MP-friendly police who turned all these assets over to the MP.
When these various catacomb churches tried to join other catacomb True Orthodox Churches, with no records, they had to submit to repeated ordinations and consecrations to create valid lines of apostolic succession with the parishioners required to undergo additional catechumenates and then be baptized or chrismated again.
Every time one small group joined a larger group, these ceremonies were repeated, meaning that the faithful could not receive the Holy Mysteries until their status was once again rectified through chrismation or another baptism. It gets tiring.
Some of these catacomb True Orthodox Churches have refused to go this route of repeated baptisms, chrismations, ordinations, and consecrations in order to create the appearance of legitimacy only to discover that another larger group still considered them to be "uncanonical."