Tahmetianity, The Tahmetian Crusades
Tahmetianity is considered by many to be a scam -- it was founded by the appearance of the same "prophet" at the same time on five different worlds, a miracle confirmed years later (relativistic travel only, and in this pre-wormhole period only light-speed messages could be sent at the time). This "miracle" caused a mass movement, a religion that gained the adherence of billions of people and seriously weakened the remnants of old-line Christianity and Islam (the "prophet" claimed to be the messenger of Jehovah/Allah). On several worlds the Tahmetian-controlled governments persecuted and even massacred believers in other types of religions, including Etodists, Undyoists, Venpredessi (a movement of ancestor-worshippers), various neopagans and even Tahmetian heretic groups. The Undyoists claimed that Tahmetianity was an elaborate scam, its founders using some secret FTL technology to organize it and later claim power. (According to the Undyoists the "prophet" was five clones designed to look similar, based on an old sequence from the Human Genome Diversity project of 2016).
The Tahmetian religion was thoroughly discredited by the efforts of Undyoist refugees in outlying worlds (and other reports of atrocities) and eventually the governments of the five worlds in question fell into disunion, attacking each other. One of the prophets was murdered by an antitheist resistance movement only to reappear alive a week later. The influence of AIs on the whole incident is debated. There are still hardcore followers of the faith, who remain very antithetical and hostile to Undyoists.