Read an interview once where he said he bolted towards the mound outta anger, got a few steps in and realized he was charging Nolan Ryan. At that point he was pot committed.
Better yet, why did he even go at him. Not the brightest guy.
I thought I remember from Facing Nolan that there was some dust up or tension from earlier and that Robin knew he was gonna get beaned and basically knew that he had to go out there.
The White Sox and Rangers hadn't been getting along at the time. Alex Fernandez plunked Texas slugger Juan Gonzalez the inning before. If Ryan wanted to retaliate (as he often did), Ventura was the logical target because his single in the first inning gave the Sox a 1-0 lead. But even before the game began (right around the time he met with the young Olympians about sportsmanship), Ventura told his teammates that if he got hit, he was going to charge the mound no matter who was out there.