Pacers need someone to fill that wing/forward slot for them and Siakam (if he gets back to 2018-19 Siakam) is one of the best in the league. They also end the Turbonis struggle. They also get out of the Warren situation

Raptors get a true starting big that fits well with their roster. They also take a flier on Warren who could be a big help if he come back and if not it'll open some cap space for them in the offseason. Picks make up the difference in player value