He wanted to leave last summer and will leave after this season ends because he wants to move back to Argentina. I don't see how is he treated badly, he got the cup medal and hopefully will get FA cup as well. Kenny is building a team and Maxi is not part of it, nothing personal, nothing unfair about it.
I think it's been a real mistake to exclude/drop Maxi. He played well last season. Scored a respectable amount of goals. None of our players has reached that many league goals this season. Not even our strikers.
New season and we dropped him immediately for the new flavour of the month. It didn't work. So we kept on with the new blood and it still didn't work. Every time Maxi has played, he's shown his worth and the outcome has generally been - benched for the next game.
It's all fair to exclude him from our future plans, but for the here and now, we've actively decided to go with players who don't deliver, instead of for example Maxi, who keeps on doing the business when given the chance. If we stick with the non-performers, that cannot be easily excused. Even less so when we don't get the results and when we struggle to score. In simple terms, it's just poor management. (Not saying we have a poor manager, just that he's managed Maxi's situation poorly.) We have rewarded the wrong things and we have made our minds up in spite of what players have shown.
There may be reasons that we don't know. Perhaps he's been injured, perhaps there's something else. We don't know. But generally, we don't bring those things up. We go with what we see. And I think, given what we have seen, that there's next to no excuse for leaving Maxi on the bench so much.