The biggest complains from huge data centers are noise, traffic, water use, and power use/impact on the grid, without the economic benefits that a large-energy-using factory would typically bring.
Depending on location, a bunch of smaller complexes spread over hundreds of square miles vs. one big one might have tolerable noise and traffic levels, particularly if they are in non-residential areas. If you can get the data center down to under, a few thousand square feet, you can literally disguise it as a house.
Water is becoming a non-issue with closed-loop systems.
Electricity is still an issue. On-site power-generation/storage can mitigate this. This is one area where a single big complex may be better than a bunch of smaller complexes.
As a sidebar: Data centers do bring in some economic benefits, the most obvious one being through taxes paid (assuming the companies didn't get any sweetheart deals to avoid taxes). But after construction is complete they don't have the ongoing payroll/head-count that a big factory has.