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.

No doubt there is exquisite engineering and process control expertise required to operate an aluminum plant. However, I imagine there is extensive need for people to "man the bellows", move this X tons from here to there, etc that require only minimal training and a clean drug test. An army of labor vs a handful of nerds to swap failed hard drives.

AFAIK, the data center employs more people. I'm not really sure why that's the case, but neither is >1k.

I'd guess that this is also an area where the perception makes a bigger difference than the reality.

How many other jobs in the area depend on being able to get their aluminum stock orders fulfilled close by?