If the Lakers want to go all in this year, they need a center and some better perimeter defense. Reaves becomes somewhat redundant. Here they get Turner, who gives them rim defense and outside shooting, and Nembhard, a decent on-ball defender and shooter.
Indiana gets Reaves to play next to Halliburton. They were likely to lose Turner this summer anyway and they manage to replace him with Poeltl, a good starting center and great rebounder. Plus they get a pick.
Raptors get a pick swap and a younger guy in Toppin.