The person that came up with this theory was named Georges Lemaître, and he was a Roman Catholic priest and scientist. Other cosmologists at the time complained that "the beginning of time implied by the Big Bang imported religious concepts into physics." In other words, they thought that the Big Bang theory implied that God created the universe at a specific time (as the Christian Bible, and other religious documents might point out).
Are you surprised by this? Why/Why not? Explain in a paragraph or so.
Origins of the Theory