As far as QAnon goes, this would be like discovering an unsecured laptop that actually belonged to the original Q and had something like IRC channel logs that they used when generating "what won't they believe" type ideas.

As for Scientology and Mormonism, they don't have explicitly historical and rational claims to truth like the Catholic Church and some sects of Judaism do. Ask a fervent Catholic or Orthodox Jew why they believe what they do and they'll say "Because it's true." As far as I know (I don't spend significant time with Mormons or Scientologists), they don't make this type of claim to be historically validated by peak reason.

> As far as I know [Mormons] don't make this type of claim to be historically validated by peak reason.

Mormons absolutely believe that their religion is backed up by history: the book of Mormon is about and ostensibly by various descendants of Old Testament figures who migrated to the Americas, culminating in the burial of golden tablets with "Reformed Egyptian" writing in upstate New York. It's obviously fiction - but that doesn't seem to make much difference.

I know both fervent Catholics who do not feel the historical accuracy of the Bible is what makes their belief in God accurate, and Mormons who believe in the literal historical accuracy of their religion.