Im not speaking for all christians obviously, but many of them seem to value style over substance. Huckabee has that way of speaking like a preacher that these people relate to. I can understand why they like him. They dont care about his past record, they dont care about Romneys flip-flopping. They hear something, and if it sounds good, hey, its good for them.
Most Americans value style over substance. It isn't just religious conservatives.