Why Pacers make this trade - They need a big capable of starting at center. Okongwu is a tad undersized as a center, but that's okay in Indiana's scheme. Defensively, Okongwu provides what the Pacers need. He's a player who can thrive in a low-usage starting situation. Additionally, Jarace Walker is ready to move into the back up power forward role.
Why Atlanta makes this trade - After trading for Porzingis, Okongwu is relegated to a bench role. Additionally, they have a young stud in Mouhamed Gueye waiting in the wings in the front court. The Hawks gain some much-needed back up power forward depth behind Jalen Johnson with Obi Toppin. Toppin would thrive with the play-making of Trae Young, the same way he has with Haliburton. The addition of Toppin allows Atlanta to play 5-out on offense 2-deep into their rotation which is legitimately scary. Of course Okongwu has a bit more value than Toppin, so they receive what should be a VERY attractive 2nd round pick since it is unprotected and belongs to the Utah Jazz who don't look to be winning games any time soon. That pick is highly likely to become pick 31 in 2027 - Atlanta doesn't have a 2nd rounder that year. It allows them to draft the best player available in the 2nd round and give them the 2nd round rookie guaranteed contract which is a gem for cap-friendliness.