The last trade doesn't make sense
So the first trade was this:
Cleveland - 1st Overall pick
Seattle - Three first round picks
Seattle Seahawks really wanted Bo in the first overall pick but obviously they saw and thought there was more value in three 1st round picks
This is how the second trade went down
Cleveland - Three first round picks, Some Punter
Seattle - 6th Overall Pick
Now the only reason Seattle made this trade was because they still wanted Bo and he dropped down to 6th. The problem is why would they give back more for Bo then they traded him for? If they saw him as that valuable they should have gotten more for him in the initial trade with Cleveland. Second if they wanted him that bad don't even trade the 1st pick overall since no one could have imagined Bo dropping like that (forget the signing bonus you make sure you get your guy). So Seattle conceded on Bo they moved on they were comfortable. They thought they had a better deal in their hands so why flip-flop. Second seattle had Costner on the ropes not the other way around. Costner bungled up the draft with his moves and was just trying to save face. Costner even dug himself into a deeper hole by trading away three 2nd rounders so if Seattle refused then Costner is left holding the bag. Seattle should have used that to their advantage. Third the Jags GM knows Seattle really wants Bo so leverage the Browns three 2nd round picks on the Hawks into four 2nd round picks from them. Would have been a better deal compared to what the Hawks made with the Browns.
Also from Costner's POV when he decided he was going to take a RB he could have attained at a much lower pick, he should have tried to trade back down to a lower draft slot like how Seattle did with him. Retain some drafts picks, salvage it as much as you can, perhaps even get back in return what you gave up if not receive more since Costner would likly trade with a team with a lower pick than 7th overall. He wouldn't look like an idiot then. Costner didn't know Bo would drop, that was inconceivable, so at that point in time that was the best move to make with no change in sight.