My thoughts are that most of the betrayed are affraid to show the full wrath of our anger for a few reasons 1) the emotions have overwhelmed us and we don't know the depths of the anger yet 2) we are afraid of being so angry and until this did not even know we could be this angry 3) we are afraid it will push our spouse further from us and more towards the AP.
And I would guess that the longer the unfaithful spend choosing between the spouse and the AP the longer it takes for the anger to come out.

Just my thoughts. I appreciate this series and think it is well needed. Thank you for all you do. Just a suggestion but maybe ending it (when you done but I hope there is more to come) with information on what happened when one or both of the parties fail to grieve.