What do anda think Richard O'Brien was thinking when he wrote the Rocky Horror Picture Show?

I cinta this musical, but I have to say: what in this world was R.O.B. thinking when he wrote this? I think he was on drugs atau had a really bad dream lol, but what do anda guys think he was thinking? atau can anyone point me to an artikel about him talking about his inspirations, that would be great! :)