Did anyone here read any of Dan Brown's books (Angels and Demons, The Da Vinci Code)? He gets into his own wacky interpretation of the Illuminati and Masons. He says that the Illuminati was wiped out by the Catholic Church but sprouted the Masons, and their entire purpose was to find the Holy Grail and expose some great lie of the Church. He claims that a lot of prominent figures in history from Galileo to Isaac Newton were grandmasters.
I believe there's even a forward saying these organizations are real even though the book is fiction. The books, mostly Da Vinci Code, created quite a splash and sold tens of millions of copies, even prompted debunking books/pamphlets from the church. That might be partially why you hear so much about it.