Derlethfags pls go
Cthulhu is a literary symbol representing the great Unknown of the universe in all it's vastness, cruelty and unknowability, Cthulhu is meant to physically represent and hammer in the central message of cosmic horror: human inconsequentiality. The universe is big, and what we don't know about it is a lot, therefore Cthulhu is big. The universe is harsh and brutal, therefore Cthulhu kills people. Cthulhu wrenches control from us with total freedom - where man shall be as the Great Old Ones, law and sanity will be cast aside, and we will learn new ways to shout and kill and revel and enjoy ourselves. It's a reversal of civilization into a bestial state, something Lovecraft himself feared would happen to society, although Cthulhu's apocalyptic presence is somewhat more extreme than 'social degeneracy'.
Cthulhu isn't real, friends, it was made up by a staunch materialist with a great imagination and concept to convey.