Property taxes. Construction jobs. The land is unused and already had tax incentives. Remember, tax incentives don’t eliminate taxes, they just reduce them for a period of time to encourage development.

Many of these data centers are demanding tax breaks from the local governments, so taxes isn't a great excuse. The construction jobs are a one off deal, most of which will be done by non-local firms that specialize in large construction projects that don't exist in areas with "unused land". And then you also have to account for the higher power costs people in the area will be paying which is just another subsidy to big business on top of the stack of them that area already paid out to big business.