In my current playthrough the Khuzait have 15 towns on autumn 9th 1087. Southern Empire is wiped out except one castle, Northern Empire lost everything. Both are left with only one clan. 4 Empire clans defected to the Khuzait, one to Sturgia, one to Aserai and probably one or two to the Western Empire, as they are the second strongest faction. In my opinion this is the main reason for snowballing. As soon as one faction looses a fief, everybody starts defecting. Super annoying.