Sure seems like the effort goes away... but maybe they're being told to turtle.
As discussed in another thread, this has been happening for YEARS. It's not just Trotz.
And if it's the players there are a few reasons this happens, beyond normal expectations of good teams sometimes coming back on you:
1) Laziness or complacency.
2) Choking.
The first cause is something that can usually be coached out of a team, but maybe not some individuals. This is the "just enough" factor Trotz talked about. It can show up due to fear of injury, wherein you do "just enough" to get to a point where you can coast. You hold back because any more "extra" effort may get you hurt and set you back. It can come from thinking you're better than you really are, or misjudging other teams. Or it can come from feeling entitled, as though you've done your job and now someone else can step up and finish.
The second cause is not related to laziness and may actually result in "trying too hard". In hockey they sometimes call it "gripping the stick too tight", and this can definitely happen with enough players that the team as a whole stops playing a loose and free style that allows for maximum performance. The other side, meanwhile, has nothing to lose and just goes for it. When an athlete chokes he's often fearful of a certain outcome and he unconsciously makes that outcome more likely by thinking too much about it, and then overthinking mechanics instead of just trusting his ability and training. If a hockey player gets up 2 goals and starts to wonder or even expect they'd blow the lead it increases the chance that it WILL happen, as he'll play differently than he normally would and react to events in ways that help that outcome to manifest. When you have enough of these chokejobs you start wanting to "get it to the clubhouse" as we say in golf, which takes you out of the aggressive "in the now" state and puts you in a defensive "when will this be over, please don't let anything bad happen" frame of mind, complete with all the negative stress reactions like muscle tightness and reduced coordination that impact your performance.
We saw the effect of the latter in Holtby over the last year as his confidence was eroded and he experience great conflicts in training and instruction that prevented him from getting into a flow state. According to radio reports, Kirk Cousins of the Redskins also has a similar performance anxiety problem, as some of us speculated here. These are otherwise talented athletes who, when lacking confidence and put under pressure, simply think too much at a time when they should be thinking even less.
tl;dr: we need a drill sergeant and a shrink