By orders of the Supreme Soviet, the Russian Orthodox Church as an official establishment on Earth was disbanded and ceased to exist; it was driven into the catacombs. He even tried to start the "Living Church", which was recognized by the heretics in Constantinople. When it became known that it would not be that simple, Stalin organized a his new R"O"C that would take orders from him - spying on orther people and countries, quite a useful tool as it turned out.
The problem is essentially that there are many people who became part of Stalins new church, and have come to beleive that this was a creation of God. They have also come to ignore and detest the Catacomb Church, and this is because people equate Earthly power with truth. But as Christ said, the one shall route the many, and the fool shall confound the wise.
And being forced to deal with Stalin's creation, which has no apostolic succession, the ROCOR has fell into the same error of recognizing them as legitimate - ignoring the true Russian Church of the Catacombs. Earthly power has such a corrupting effect on weak men.
But "for this cause, God shall send them a working of delusion that they should believe a lie, so that they all may be judged who believed not the truth, but had pleasure in unrighteousness".