Good genetics, and more importantly great food sources available (nutrition, nutrition, nutrition). That deer is the result of both of the previous.

As for aging deer, I never take into consideration the antlers. They can be deceiving and very influential in the decision process. However, that is a great deer, and I would never slam anyone for taking the opportunity to take such a magnificent animal...but could you possibly imagine what kind of headgear he would have sported in say two or more years.

GREAT DEER and CONGRATS!!!