Warriors: They get a stretch five that will pair very well with Draymond, Steph, and Jimmy, when he comes back. Myles Turner has not looked great this season, but has had to be the second option on a disappointing Bucks team. He has strived when he is in a smaller role and playing with Steph and Jimmy will help him greatly. They also get rid of Kuminga and Horford hasn't provided much for the Warriors this year.
Bucks: They get off the Kuzma and Turner contracts and make Giannis happy with another start next to him. They are both injured for a significant amount of time, so having this offseason to build around those two players will help them prep for an attempt at a run next year. They also don't have to give up any picks which is big for a team that will eventually head towards a rebuild after life without Giannis.
Mavericks: They have been looking to move towards a rebuild Harrison screwed everything up. They get off the Davis contract, after he has been unavailable for them. They also get a piece to build around around Cooper Flagg and if it doesn't work they can just decline his team option. Kuzma can also just walk in free agency and they can buyout Horford. They also get a first round pick that might be good, as the Warriors will struggle without Jimmy for the rest of the season.
In conclusion, the Warriors get rid of Kuminga and get a stretch big. The Bucks attempt to keep Giannis happy. The Mavericks get a lot of flexibility. They can resign Kuminga or get rid of him at the end of the season and clear up a large amount of cap space.