Definitely fun to read that you picked up on it this way. We played a lot of sim, management and strategy games as inspiration, and XCOM (and other games such as Civ) was definitely a big one! We've pulled a lot of inspiration from other games, too! One of the stranger (but also major) sources of inspiration is Binding of Isaac.
Hope you're enjoying the game! It's awesome to have it be compared to a game as insanely great as XCOM. Trust me, when that came out nobody really showed up at the office for a few days.
If a village gets too many resources too fast (the difference between the resources available and in use it too great, you can tell by the red arrows next to a resource in the city view) they will grow more greedy. The amount of angry red greedy faces in the city view or the little face in the Ctrl data-layer shows how greedy a city is.
Greed can either lead to a village wanting to sack another village (start a war) or attack your Giants. If a village successfully destroys another village, they will gain a War Marker, which makes their army stronger.