They didn't take my town

[dminoz]

Playing as Cordoba, I had the town of Porto assaulted by Crusaders. I chose to lead the defence, and lost. The Crusaders breached the gates and killed my entire force in the town. The defeat screen came up. But they didn't take the town; instead they carried on touring around the province, plundering. This happened twice.

So, my question is: why didn't they take the town? Did the AI decide that there was a downside to taking the town that it didn't want to take on? Did it just want to plunder?

Or did the failure to take the town arise from a glitch?

I'm using the Holy Rome mod, if that makes any difference.

[Elvain]

The mod doesn't make difference in this case.

When crusader army conquers a city it has 2 options to pillage it and (second I forgot). If the player or Ai decides to pillage it, it still belongs to former user.
The other choice creates independent state which is vassal of crusader's former king. And this new kingdom would be at war with you.
I don't know why AI uses pillaging so often

[Angryminer]

The crusader's king can decide to either take the town and make it a vasall or just plunder it, giving the crusader's nation some amount of money.
So my closing statement: It's not a bug, it's a feature.

Angryminer