They were never presented as a secret society by any means.
I mean, they went around openly advertising who they were, publicly fundraising, and telling everybody in the Marches who would listen to their pitch what they were all about, via increasingly sophisticated marketing material.
As far as we know, the weird location of the Fulacin building was just some wacky coincidence -- or perhaps the result of Ancients related residual psionic hoodoo. Who knows? Perhaps the most uncanny thing about it is the Droyne graffiti carved all over the place -- that, and the fact that the wooden floors haven't completely caved in after nearly 800 years of general neglect.