It's best if you reserve the term "conspiracy theory" for grand conspiracy theories, which require secret coordination on implausible scales.

The theory here is merely that an influential socialite (what Maxwell was regularly described as before her arrest) was a reddit addict powermod, that some people running reddit were aware of her identity - not necessarily knowing anything about Maxwell's wider social network or the activities she was convicted of.

Nothing here is especially implausible. It may or may not be correct, but it's not a grand conspiracy theory, just a theory of everyday shady non-public coordination. It's no more a conspiracy theory than it it's a conspiracy theory that some people in your town sell drugs (yes, they do, and technically they have to engage in "criminal conspiracy" to do so, but we don't call people conspiracy theorists for believing it happens).