The tactic of a ground and pound is to catch the opponent off gaurd and to push them backwards while tripping them with your leg so they land flat on their back, knocking the wind out of them, then pouncing on top, pinning the arms, then beating their face in in just a matter of a few seconds. It can happen real quick.
George wasn’t a fighter. A pudgy fellow who always feared getting too close to those he would follow/report in his Neighborhood Watch duties. If his intent was to shoot and kill Trayvon, no way he picks a fight with him just to risk getting subdued and pummelled so he can have an excuse to shoot him. It’s crazy to even try to understand that.