Every coach benches/demotes young players at times to send a message.
The next coach, especially a veteran HC, is sure to do similar things.
Trotz has done so on the Islanders. I'm sure he did so on the Caps and Preds.
HCs have to manage 20 players over an 82 game season (and hopefully, playoffs), there are times when players are coddled and times when they're spanked. Some coaches are known as disciplinarians, some as "player coaches." Very few are able to maintain a team's attention over the long run - though that's also partially the job of the GM, to provide enough self-motivated players with leadership skills in the clubhouse that the coach doesn't have to spend all his time nurse maiding fragile egos.
HCs have to scheme, motivate, and manage games. Few are good at all three, and even those that are, often have an expiration date.
After watching Lavi fail, Berube take the same players and make the playoffs, Berube fail, Hakstol take the same players and make the playoffs . . . and now watching Berube carry the Blues into the playoffs - you'd think people around here would be a tad more humble in their coaching evaluations - Babcock and Lavi, despite being given talented rosters, may not get out of the first round (3rd time the charm for Babcock).