Copy pasting a reply I made in the comments below to a comment stating that the Hawks need a center:

They have both Landale and Veesaar at Center who would both benefit from the additional [development] minutes each would receive. Also, although he plays center occasionally, Okongwu is a 4 and the Hawks just got Lu Dort and already have Jalen Johnson so Okongwu is now the odd man out and overpaid for what he would be on their squad (a bench player)

That being said, the Hawks could add a 4th team and receive a center from them in exchange for the assets they are currently receiving in this proposed trade.