Perhaps initially, though today any religious influence is merely the result of organizational interia, not genuine concern for the opinions of Christians.

But I don't think that's the only reason. My thought is that there would be concern over connections to actual criminal activity (human trafficking, abuse, revenge porn, etc). I'm not saying all porn is those things, but I imagine it might be harder to be sure porn isn't connected to those things.

Edit: I think pram probably has it right.