Wolfsburg had big plans for this season, aiming for the title. I guess that's why they refused to sell Dzeko in the summer.
At mid-season they saw that they won't compete for the top and they felt safe in mid-table, so they sold him. Unfortunately for them, they made a mistake because that mid-term sale might result with losing more than they got from Dzeko's sale if they fall to Bundesliga 2.
They fucked it up badly and for that I'd gladly see them relegated.