>and that it is reminiscent of the end of the Roman Empire

What a totally ridiculous comparison. The roman empire always was an explicit a dictatorial state. Its end took hundreds of years of internal and external forces tearing it apart as coherent entity. Characterizing it as two factions fighting for power is just bizarre.

Maybe he meant the of the Roman Republic, like with the optimates and so on.

That’s far from accurate. Augustus positioned himself as the restorer of the Republic after a horrific period of civil war, and cobbled together his authority from existing Republican magistracies, especially the Tribune of the Plebs. The Julio-Claudians at least attempted to maintain the fiction that the Republic was still functioning. Explicitly dictatorial it wasn’t, although actually dictatorial it certainly was.

The end of the Roman Empire was due to a civil war, where the Church was one of the parties embraced by Constantin.