I don't think it's down to porn, but porn is a key influencer.
That doesn't mean porn invented pubic hair removal any more than it invented strangulation or anal sex, but it is a pervasive influencer whether people like it or not.
It works by suggesting to men how sex should (or could be), which then filters down to women being asked 'oh, it might be sexy if you shaved, tried anal etc' Eventually enough women find that their men are 'pleased' by it that they become conditioned to think that it makes them attractive to men. Eventually, society then accepts 'shaved is attractive' and a positive thing.
That is not to say ALL women do this, or all men, but it's an example of how pervasive porn can be in changing public perception and behaviour.
It's not only porn of course, advertisers for fashion and beauty products are hugely influential too, and can steer large swathes of the public into curly perms or out of them. Into shoulder pads or out of them, into body hair or away from it.
There's a much larger market for grooming products than ever before and thus it's no surprise that smooth bodies are marketed as 'desirable' to us.
Nobody's saying it's never happened before, of course it has. But given pornography is one of the highest used sectors of the internet, you'd be a fool to underestimate its influence.
Advertisers would kill for the reach and exposure that pornography has.