I have no idea how the move to Mishin can be rated. Would things have been better with another coach? Who knows?
I am not a big fan of Lambiel, the coach, although he definitely improved Shoma Uno a lot in "advanced" age. But there is something about Lambiel that very much rubs me the wrong way. He never takes himself back... and he transforms skaters into mini-Lambiels, in my, very subjective view, robbing them of their individuality. Shoma before Lambiel was worse but I liked him better. I don't want to be mean or anything, but my very personal opinion is that it's almost creepy when his skaters start to imitate his looks. Not that Mishin is unproblematic... but to me it looks like he leaves his skaters some room to breath (as skaters). I like that he works with several choreographers who bring in different styles. And I think that Kolyada's style was kept during his Mishin time. His programs felt good for him, in fact White Crow was his masterpiece, and I also enjoyed Schnittke's Tango. I did not get the feeling that these are Mishin's programs that he imposed on Misha. So there's that at least.
Also, if we are talking about Lambiel as a possibility and take Shoma as a point of reference, Shoma has always had great potential but it was all messy. Misha was never messy. He just wasn't consistent. So I'm not sure the same solution would have been possible to apply.
Maybe a very down-to-earth coach like Huth could have helped, but that might be my German bias speaking there.
Let's be honest though, he would not have moved to a coach outside of Russia anyway, likely for personal reasons, and also because the fed would not have supported that at all.
But you seem to think that he could have gone to the Olympics and that he was deliberately screwed over by the team. What makes you think that? I don't think that's what happened. I think Mishin has huge respect for Kolyada and would not have preferred Semenenko to go if Misha had been able to.
Anyway... him stopping hurt me, too. He's one of the skaters hanging on my wall... on a photo, but I even painted him.

In his White Crow balletic turn, which is so beautiful and so him. Messed up his fingers a bit, they seem pretty long now.
I hope to see him in the next show tournament. I am quite disappointed that I cannot understand his commentary, because I'm sure it's interesting.