I saw that the Kings are interested in Jrue Holiday. If they are looking to acquire him, they obviously want try and use their current roster to try and make they playoffs next year without giving up to much. This trade would make sense for all parties involved. More breakdown below:

Kings: So the Kings want Jrue, and are willing to take on his contract, they are going to need to move other pieces to make the money work. In this one, Valenciunas gets moved cause his contract works and moving Monk keeps them under the first Apron to make other moves. They get Terrance Mann to replace the guard scoring off the bench, and can use the TPE to not have to pay his contract. They give up their second to Boston and a protected first to the Hawks (My guess on how the picks would work, I'm bad at pick value)

Celtics: I think they would love this trade. They get off of Jrue's contract and get under the Second Apron. Valanciunas can replace the Horford/Kornet minutes and is cheap. Queta to the Hawks just frees up a little money Apron space to work with. I think they only other thing is Boston may want a guard to replace Jrue's minutes, but neither team had a guard cheap enough to keep them under the 2nd Apron that I think ATL or SAC would be willing to give up. Getting under the 2nd Apron allows them to make more advantageous moves if they want to do something else though, like maybe in a Porzingis trade.

Hawks: Atlanta would probably revel in the chance to get Malik Monk. He would perfectly replace Caris LeVert off the bench, and is better. Seeing how well Caris played in Atlanta, I think Monk would thrive. They get Queta as a bench option, get off of Terrance Mann's contract, and a few picks to boot by taking on Monk's contract. In all of this, they are able to use TPE to not have to add any Apron money. Maybe they need to send other picks back (again, i'm bad at valuing picks in trades)