Not only would I suspect that an aluminum plant employs far more people, it is an attainable job. Presumably minimal qualifications for some menial tasks, whereas you might need a certain level of education/training to get a more prestigious and out of reach job at a datacenter.
Easier for a politician to latch onto manufacturing jobs.
I'm pretty sure both the plant and the DC have both "menial" jobs and highly-skilled jobs.
You don't just chuck ore into a furnace and wait for a few seconds in reality.