How does the AI choose a new capital?

[Mitchz95]

I had a neighboring empire lose their homeworld to a supernova (via a mod) and they had to choose a new capital afterward. They had nine other planets in their empire, most of them fairly well-developed. Do you know which one they chose?

A tomb world. One they hadn't even finished colonizing yet.

What gives?

 

[OrigamiPhoenix]

I'd like to know this, too. Given how the trade route system needs to funnel into the capital, it's really counterproductive that they pick an isolated system inside their rival's empire as their capital.