As I recall, Hak had been a head coach in the USHL for about four years before coming over to UND. After just a single season at UND, he was named "Associate Head Coach" which I interpret as sort of being second in command. At that point I think Berry had only been at UND for maybe a year or so, and had no head coaching or professional coaching experience, so Hak seems like the natural selection for Blais to name as Associate Head Coach.
Blais obviously left under good circumstances, and wasn't fired, so I'm sure any support he gave for Hak being named his successor would be given some weight.
Then, after Blais left, and Berry spent a few years as an assistant, he went on to be an assistant at the professional level, before returning. Once he returned, he spent another year as an assistant, and was then named "Associate Head Coach." Thus, when Hak left, again under good terms, I assume his selection of Berry as Associate Head Coach, and any positive comments he made about Berry, carried some weight.