Pels want to build a defensive identity, pj works great with queen as a frontcourt partner and even as a small ball 5 currently with his floor spacing and defense. A package surrounding more picks would be ideal however due to the risacher trade, the mavs have no SRPs to give up and I don't think the value difference is large enough to include a swap. Klay would likely agree to a buyout.
The Mavs get Murray who works great as a backcourt partner to Kyrie with defence and playmaking, instantly making the Mavs better and a fringe contender. They are reportedly aiming to part ways with Klay so it seems likely he would be included in a deal like this to make money work. Pj getting traded also seems likely to give more game time to morez Johnson jr.