They also know more than most all coaches THINK they know. Take a referees course and see how well you do with the test. As a coach for a few decades I did one year and was awakened as to how many of the rules I had inturpreted wrong. Rules I thought were there but were not. I have a lot more respecct for the game now and most officiating. Now this is not to say their are not bad refs out there as we know there is. There are also refs out there who are there just for the paycheck and I do mean that litterly. Lots of the older ones using it as a second income and some can not even keep up with the play but their ranking keeps them there.
The view from the stands differ from the view from the bench and they differ from the players on the ice as they differ from the view of the ref, so when a situation is viewed from the stands it will differ from the view on the ice or may not even be seen as there are more obstructions in the view of the ref,/nets, other players.