My thoughts:
Monty is a frontrunner - great guy when things are going well - and jumped out to a great start in the 22-23 season when there weren't great expectations for that team and no pressure on him. Tactically a good coach. His breakouts and attacking style made the best of his roster.
The problem is mentally he's weak. The big moments get to him, he goes into full panic mode come playoff time, and more than anyone he carries the weight of responsibility for the collapse that year. Fiddling around with the lines after great road victories in games 3 and 4, seeing a goalie who was clearly and obviously injured and waiting six games to make a change (and this isn't just a matter of leaving Ullmark to dry, it's also throwing Jeremy Swayman to the wolves by putting him in ice cold after two weeks into a do or die winner takes all game.). Benching Grzelcyk as punishment when Ullmark gave the pick away in overtime of game 5, then watching Clifton get beat over and over in game 6. Etc, etc.
I'd be more forgiving of that if Jim showed any accountability at all over that. But every press conference was deflecting blame, like "ask Goalie Bob". His interviews from earlier this year when things were going bad showed more of that attitude.
When the team is doing well, he's a great guy to have around and practically a motivational speaker. When things turn south, you get a guy who runs from responsibility and passes the blame around.
My opinion of how things went down this year is that Sweeney wasn't willing to commit to him long term so extension talks were slow and they were waiting to see how the team performed with the additions to the roster. He then went and signed guys like Lindholm who didn't fit well into the preexisting system. That plus the Swayman situation made training camp a complete disaster and I think Monty became more and more aloof from the team. And the elephant in the room is that I am 99.999% sure that there was some tampering going on with Monty and Doug Armstrong. Who reached out to who first is up in the air, but knowing that extension talks were not progressing, plus the fact that Jim and his wife had a fondness for the St. Louis area, I'm sure that they were talking and Monty had a job lined up. And since the team lost a lot of guys to retirement and free agency and stumbled out of the gates and he saw greener pastures. Wouldn't be bold enough to say he tanked it intentionally to get fired, but I am confident that his heart wasn't into fixing things here and he was checked out for the first few months knowing that if he was fired he'd have the job he really wanted within a week.