Why for Indy? The J.O. era is done, time to move on., They've needed a point guard upgrade for a while now, and Ford could be the man for the job.
Why for Toronto? Calderon has made Ford expendable. They need some front court help if they're ever gonna go anywhere in the playoffs. J.O. is an elite defender who can score and rebound at a fairly high level. A great front court partner for Bosh. Harrison is another big body and is more talented than any of the filler players for Toronto.
Both players are injury risks, so it works out fine.