While overall you have some wise thoughts, I can't agree with you on this one.You say that but there was no sign of that burnout in the first half of his only full season when we beat Marseille at home, thus topping the group. But we fell away very quickly and quite alarmingly after that match in that season.
I think there was plenty of signs of a mental burnout way before topping the group (that everyone in the entire world expected us to top btw).
Results wise we had a very strong start to the season but our football was light years from the one in 22/23. A lot of this came down to the sales of Caicedo and Mac Allister, but some of it did not. Most worryingly, the defence looked horseshit and there was little to no signs that anyone really cared. "These results will happen sometimes with a manager like..." was the reasoning and everyone happily accepted this "new way of seeing things" invented after the Everton loss in the spring that year. Unfortunately neither our own players or the opponent teams seemed to shrug about it.
We looked a little bit hung over. Not giving a shit about some of the "lesser" games, underestimating opponents etc. Honestly pretty normal stuff and I agree with @jackalbion that this was inevitable/difficult to deal with. It happens SO often when a smaller club in a big league takes their firsts steps into Europe.
The manager certainly didn't help though. One of the most baffling decisions must have been to remove Dahoud from the team despite the excellent results we had with him.
I opposed the signing of Mahmoud Dahoud before it even happened. But when he came to the club, signed to start games, I thought "ok, lets go with that until something better pops up".
But when Dahoud in his first 15 games only had recorded one loss (against Chelsea in the League Cup) I thought "ok, it works, I admit". Then, seemingly out of nowhere, we say "f*** this guy who helps us get 2.11 points per game in the league" before spending the rest of the season moaning about a lack of midfielders and only winning in the league every second month.
Winning the EL group stage was easy and something all English teams need to do or they've underperformed. The results were nice in the league before we decided to stop winning. But the football itself was stale, unenergetic and riddled with fear from day one against Luton. Perhaps not physically burned out from the start, but seemingly mentally. When the self-playing piano finally found itself in need of a tuning, there was no one around who was capable to do it.