Wish I could do a few more things "wrong" like that!
From watching Rick over the years, these are the things I have noticed that probably contribute to his success. From reading books and watching videos of Howard Hill, I think he had the same attributes.
1. He is very calm. I don't think he feels pressure or becomes nervous when competing or hunting. From talking with him, i don't think these are challenges he has overcome; he just doesn't seem to be susceptible to them, in the same way some people are not susceptible to poison oak.
2. He is very strong. His bow arm is solid. In the video you referenced, I have no doubt he was shooting a bow in the 50# + range, and usually competes with the same bow he hunts with. As he gets older, this may change, if he continues to compete.
3. He is not rigid in his form, and neither was Howard. If anything, Rick is more methodical in his form than Howard was, but neither seemed to be bothered by variations from shot to shot, so long as the arrow ended up where they were aiming it.