A lot of fetishes develop from relationship exploration. A lot, maybe even most, people can get by with vanilla all their lives and never miss out.
Anal used to be a hangup for me when I started in porn, and my personal progression is probably something not to be emulated by most boys either. My personality is such that I seek out new stuff, and eventually I found anal, and started enjoying it, and doubly so with a partner that is trained or open to it.
First off, there are a lot of nerve ending involved anatomically with anal. Almost as many as with clit stimulation. Obviously different nerves, but still very sensitive. This can be good and bad, and why communication is important. I've been told that anal orgasms are more powerful and full body than clit/vag orgasms. I want to believe this, but I think the proof to me was the enthusiasm.
Second, anal in porn is not real anal, in the sense that any woman is able to be bent over and pounded at a moments notice. It definitely takes planning and good prep can make or break it.
As for male pleasure, it is probably more mental than physical, in that the knowing what is happening is way more powerful than the feelings. But when a woman is into anal and is giving it her all to enjoy the pleasure, the mental stimulation can be enough.
It's not for everybody and I feel bad for people that are turned off on it due to one or more bad experiences. Communication is key for all fetishes IRL.
In games I like the view of anal.