It could have been a situation where they simply miscalculated during a summer where Tarasenko was made available in the Seattle draft and feelings were hurt. He must have felt vulnerable being doubted and devalued. Issues with the first surgeries and being made available likely injured Tarasenko's sense of justice leading to a principled push to get traded. But when it didn't work, another strong driving force to compete with his sense of justice kicked in, pride of pure on-ice professionalism.
He was exposed at the expansion draft after his public trade request.
He went public about wanting out of St. Louis the night Tampa Bay lifted the Cup on July 7. It was later reported that he made the request to the team during exit interviews after we were eliminated in May. We made the decision to expose him in the expansion draft on July 18.
When he returned from surgery in 2020/21, his TOI per game was 5th among Blues forwards even though he very much didn't look like his old self. It was 4th during the playoffs that year despite being held off the scoresheet until the final game and finishing the series with a team-worst -8. He was given every opportunity to succeed in 2020/21 and didn't manage to shake the rust off.
Any offseason 'devaluing' was a direct result of his trade request. His trade request was not a result of us devaluing him in 2020/21 or that offseason. He very well may have made the request because he felt that the Blues doubted him or devalued him by providing poor medical care in prior years. but his request absolutely wasn't the result of feeling spurned in the summer.
I want to stress that I don't have any problem with Tarasenko trying to get himself to another team and I have an enormous amount of respect for his professionalism in the 15+ months since he made the attempt. I wear my #91 jersey more than any of my other jerseys and I think players should advocate for what they believe is in their best interest. I will harbor absolutely zero ill-will toward him if he simply plays out his contract and walks (even if that means he refuses to waive his NTC for a trade that could help the team). He has honored his contract and given 100% of what any pro team could reasonably expect. No matter what happens, I don't think any other Blue should wear #91.