Their 100% high quality diet is noticeable in the taste. The massage and lack of strenuous activity reduces amount of and softens collagen which is mostly tasteless but rubbery. The other major factor is the hundreds of years of selective breeding.
I've had those Kobe beefburgers, btw. Despite my doubts they turned out to be very tasty. The distinctive taste came through and stayed with me like a good meal does. I think it's more a matter of preparation skill. You can ruin a steak just as much as a hamburger.