You might as well ask what's so great about the Harry Potter books, why people like Wes Anderson Films, or how come Lost is such a popular show. Because people have different opinions about stuff than you and like his music, that's why. What on earth do you need to know besides that?
I suppose if you want, you can really dig and research and come up with information on what sort of evolutionary thing took place that makes people appreciate music in the first place, and some theories on what sort of genetic make up or cultural backgrounds makes certain groups of people like one type of music over the other. I don't know any of that stuff, though . . . all I know is it's fun to dance to Thriller.