Why do countries in an opposing alliance seem to focus on only one resource?

I’m currently fighting a coalition and noticed something unusual. Most of the countries in their alliance seem relatively new, and each one appears to be upgrading Arms Industries mainly in cities that produce a single type of resource.

It almost looks like each country is specializing in one resource and possibly trading resources between themselves.

Is this a common coalition strategy, or could these be multiple/bot accounts controlled by the same person?