How - "so"? To some extent, everyone is attracted, of course. There are other fetishes, but this one is the most versatile. However, not everyone has it in the first place.
It's all individual. My friend, for example, loves absolutely flat ladies, sees aesthetics in this. And a young man always forbids me to go on a diet and tries to fatten, says he loves when there is something to hold on to.
(Most) men are indeed attracted to the physiological and psychological differences of the opposite sex. This is how the action of the basic instinct manifests itself.
If the author of the question means whether men are attracted only (exclusively) by the buttocks, then I have to disappoint ugly women.
Men are really attracted to the buttocks.
They are also attracted to breasts, legs, hips, feet, eyes, noses, etc
And some men like other men
Total disruption of the covers
hahahah) they definitely have something) besides, in recent years, the fashion for breasts has slowly turned into fashion for the buttocks and their image has become more advertised and fall into young men's hearts.