No state income tax, fewer regulations (zoning, environmental regulations) than other parts of the country, relatively cheap power, large existing industrial base. For skilled labor that last bit is important. Also one of the cheapest states wrt minimum wage (same as federal, nothing added), which is important for unskilled labor.

Depending on the part of the state, relatively low costs of living which is helpful if you don't like paying people much. Large areas that are relatively undeveloped or underdeveloped which can mean cheaper land.