The cavs won this trade because Lebron is still on the team but lost if Lebron moves on. Out of both players Irving is the more valuable because he is arguably just as good on offense but can be better on D than IT. Irving's size means he can be on the floor in the final minutes defending the lead whereas IT provides no defensive upside. The Cavs are deeper now and should be able to match up better against GS. Not sure if IT remains a scoring guard if that is going to result in the cavs being better. They need a floor general more than another assassin and role players who can shoot and defend.
Most of all the Cavs need a better coach.
In terms of accounting for LeBron leaving, I think this was the best they were going to do.
This draft is very top heavy, and I don't see Brooklyn improving. Adding Russell, Mozgov, Carroll, Crabbe doesn't move the needle for me, a lot of those players are negatives. Then you account for the loss of Lopez. There is a very strong possibility of getting one of the 3 elite prospects in this draft.
Phoenix was never going to give up Josh Jackson, and none of the other rumored teams had a better piece on the table than this pick, IMO. I know that they also pushed the Celtics for Tatum, so in that context Boston did well in retaining the right assets. Boston also still has that Lakers pick to work with.