There is obviously friction for the reasons you stated.
But, that's not why he asked to be traded.
All that was happening during the Season.
He didn't ask for a trade until he realized he wasn't getting that 10 mil bump in salary this year.
Via Jon Krawczynski of The Athletic:
There were reports of friction between Butler, Towns and Wiggins, but sources say that is not the main reason Butler has decided to move on. Butler was hoping for a renegotiation and extension of his contract this summer, one that would have raised his salary for 2018-19 to $30 million and added another four years and $145 million on to that. But the Timberwolves would have had to cut an enormous amount of salary to pull that off and deemed it unreasonable if they wanted to stay competitive in the near term.
I wonder if Butler asked to renegotiate to give him an excuse to demand a trade?
What I mean by that is, to demand a trade because of friction between him and his teammates would be bad optics and could cause teams to shy away from him, making it more difficult to move him (like the Wolves trade demands are currently doing).
But if he knew the Wolves weren't going to pay him, he demands a trade, claims it's about money and he doesn't look like a guy who can't get along with his teammates.