Because the Bucks invested more than the state.
Are you a socialist? Do you think all property belongs to the state?
Wisconsin is on the hook for the current stadium. By investing some money, they will get a positive return and be relieved of the liability the existing stadium places on taxpayers.
It is a win-win all around
So when the state pays out $20,000 it's a welfare parasite. When they pay out 2,000 times as much then it's good business. It's all clear now.