The playoffs made it apparent that Sharpe doesn't have a long-term fit on Portland's roster. In this scenario, the Blazers move off of Sharp to free up a little cap space, while also receiving the 15th pick in return. This allows them some cap flexibility, as well as allows them to target a more complimentary player for their roster via the draft, or via trade with the additional asset.
For the Bulls, they use the second of their two first round picks to bring in a young, 20-point per game scorer, and gamble that Sharpe's unmatched athleticism has some untapped potential.