Only Matheny can answer that.
The Royals' expectations are different than the Cardinals', so I could see him blooming in a situation that does not have the often-heavy burden of always winning, especially when you wear that as a manager and a former player.
I imagine his interactions with media would be better, considering those expectations.
He would also be out from the TLR shadow, which is not easy for anyone to live under, especially the next man up, when he's not really comfortable with it.
My biggest question would be how he handles a young, rebuilding team. His tendency here -- especially as he was faced with the challenge of managing players he played with and against -- was to lean toward veterans instead of young players.
Baseball is moving in the opposite direction.
If the manager of a team that is going to prioritize youth is not on board with that, there could be complications.
If he gets the job, I wish him the best.
We didn't always see eye to eye, and clashed more than a few times, but I think we all learn a lot as we go along. I know I have, and there are some things I regret in how it all played out. There are also some things I think he would be wise to learn from on his side of the desk.