You can never really know why something a hockey coach does starts to annoy fans sometimes. Well, you can usually guess. Look at the results. Were they good or bad, and if they were bad, you’ll find a lot of people deciding independently that whatever the coach did was obviously wrong and should be changed. It’s not exactly unusual to find coaches who make decisions the same way.
Player on a shooting draught? Fourth line! Goalie with some bad results? Waive him! Turn the puck over? Benched. Take two penalties in one game? Press box for life! Most people can come up with examples of extremely results-based coaches doing things that had no relationship to the reality of a player’s actual play.