Know yourself and know your enemy. The current crew is looking for members who won't backstab them. Killua's trying to understand things in order to predict such events and prepare his friends for when it happens.

Overanalysing to me is synonymous with overthinking. It's not "over-" unless you wrongly predicted them by giving them too much credit (or not enough, depending on how you look at it). Hisoka's the one with the upper hand here.