I agree that this is part of it. But there's a wide spectrum available here. It's not as if the only options in the third period are, "step on their necks and bury them" and, "I'm scared of the puck".
Every one of these players has gone through multiple tiers of hockey, with multiple coaching styles. It's not a foreign language to them, adapting strategy to the situation at hand. And the one thing that confuses me the most is Lalonde - he came from Tampa, whose ENTIRE STYLE was predicated on the perfect balance of solid defense and dangerous counter punching when the opponent made a mistake. That's not at all the same as completely turtling up when you have a lead, so where's that element now that he's in Detroit? I understand the personnel isn't the same, but if the guys here are good enough to get a 5-1 lead, then they're certainly good enough to execute a better system of closing out a game than what we've seen.
Even if confidence could use a boost, it's mind boggling that all these professional players and staff seem to have zero nuance. Hire a damn consultant if need be, but this "light switch hockey" is a horrible way to approach defending a lead.
I'm with @JediOrderPizza on this in thinking the coaches aren't telling these guys to sit back. I remember Blashill talked about it, too. He talked about telling them to keep pushing but they would just tighten up and get more conservative.
A little before my post @Pavels Dog asks if we blame the other team for sitting back when the Wings push hard late in a game and...yeah, we probably should. At least a bit. I'd be willing to bet that if we visited the GDTs of a lot of teams they would have similar complaints about their teams in similar situations I doubt that many coaches are pulling in the reins, and I'd be willing to bet a lot of it is on the players just being human.
Now, I think it's fair to knock a coach for not getting guys to buy in, to a degree. But to really get buy in, I think the players have to experience success with it. But to be successful, they have to buy in. So it is a bit of a catch-22. And even Bowman had issues with it. We saw guys like Ciccarelli and Burr moved out largely because they wouldn't or couldn't buy in.