Why ORL do it:
They get a reliable Point Guard that can organize their offense
Tyus would receive an extension and be the starting PG while they wait for Black's development
He's a good shooter to space the floor for Paolo and Wagner
Fultz is a bad fit as their young cornerstones demand more and more the ball on their hands
Now that Orlando is starting to compete, they wouldn't have a place for a late first rookie in their rotation next season so they use the pick for trades instead
Why WAS do it:
Add one first round pick next draft to fasten their young movement
They can extend Fultz and give him the starting PG spot short-term depending on the players they draft
They help Tyus go to a young upcoming team that he'll start and receive an extension