IMO rapists have something fundamentally missing inside them, in the same way psychopaths seem to lack a "soul". I've had second hand contact with a sexual predator who victimised my friend by drugging her. Unfortunately I didn't realise what was going on at the time and couldn't protect her.
There was just something totally wrong with him. He was extremely awkward, talked about weird topics and had "empty" eyes.
I found it genuinely horrifying later to think that this pathetic man had been planning to rape a woman for ages. He'd rehearsed and planned out everything he did that night - he had no connection to my friend and seemingly picked her at random. To think he must have spent a significant amount of his free time getting supplies and the logistics to rape women rather than just doing all the things normal men do in their free time absolutely repulses me.
To rape someone goes against every natural empathic and protective impulse any normal human being feels towards others, especially those who are physically weaker.
Anyway, with sexual activity, most people enjoy the physical sensations of sex and the emotional intimacy. That's normal.
On the other hand, rape is intrinsically different to sex. They're really not the same thing, even if the act is superficially similar. Rapists are usually fixated with violence, exerting control over others and violating them in the worst way they can. It's a sadistic thing.
Imagine your best female friend or relative, and then imagine her in the most terrible distress - distress you are deliberately causing. It's a thought that makes you feel nauseous as a normal man. A rapist would relish the thought of causing that anguish.
Often they hate women, and that spurs them to act in such a vile way. Many serial killers and more violent psychopaths show rapist tendencies for the sadism reasons too.
I suppose you might get a really desperate loser hate women more and more, develop sadistic tendencies and so become a rapist. Usually though, it's men who are really mentally f***ed up that act like that almost uncontrollably from an early age.
I'd say simplifying it to "access" for losers is a gross misunderstanding of the kind of people who do this.