This is because of what the comment you’re replying to was saying. Aluminum was a scarce resource prior to the electrolytic process being invented that made it “distillable from common rocks.”

The cap on the washington monument is aluminum, because at the time it was still a precious metal.

The guy who figured out how to electrolyze it out of ore went on to create the main company in the US that produced it, and chose to call it aluminum instead of aluminium, thus leading to the split in spelling. That story may be apocryphal though.