A Louisiana state legislative committee was about to consider a bill in April 2024 when Richard Nelson, then the state’s revenue secretary, received an urgent message from Gov. Jeff Landry. Get the bill passed, the newly elected Republican governor told him, because they needed it for something else.

Mr. Nelson walked across a room in Baton Rouge’s towering State Capitol to the bill’s author, Chris Turner, a Republican state representative.

“‘Hey, we need to hijack your bill,’” Mr. Nelson told Mr. Turner. “‘I can’t really tell you what it’s about. All I can tell you is that it’s important.’”

Mr. Turner agreed. The bill had started out as a tax rebate for fiber-optic equipment. But when it was voted on by the state House of Representatives less than two months later, it had become a tax rebate for equipment used in data centers.

Mr. Turner had helped land the largest development in Louisiana’s history: A $50 billion data center for the Silicon Valley giant Meta that planners say could cover about six square miles and use seven times as much energy as New Orleans.

Meta wanted the rebate to build its data center in Richland Parish, an impoverished farming community in Louisiana’s northeast corner. The tech company also needed a secret deal done quickly, and state officials were eager to oblige.