Crazy Large Army Defending Riga

I was playing as Denmark and seeing how my faction leader just captured Oslo and Stockholm and that I could call a crusade on Riga, i did. I thought it would be an easy way to get a huge army since it is a village and has no walls. The crusade is called and when I come close to it i see it has a full stack garrison. Twenty units.... BIGGER THAN MY CRUSADER ARMY. That is some crazy army defending a small village... it is like bigger than two thirds of the Polish military. I sneak a spy in there and i see that it is made of spear militia and peasant archers but still.... twenty units. I am positive that noone has taken the village and let it revolt since the provinces surrounding it are still rebel. Has anyone seen this problem?

You playing with the patch? If not it could be part of that passive AI bug. Troops just loitering around.

I can't understand how it could happen - slave AI is coded to not do squat. Not build, not move, not attack, just sit there and wait to be taken over.

Perhaps a Russian army rebelled next to it and they joined forces ? Or maybe it's a crusade specific mechanic I haven't come across yet that boosts crusade target defense is said target is not owned by a real faction (else crusades would be too easy early on).

I've seen brigands move into town garrisons (it gave edessa a 15 unit garisson at about turn 20 in my venitian game) so that may have been the cause.