While a detailed theory of how alliances in EVE disintegrate may provide some academic amusement, it doesn't offer any practical guidance. If handled with naivete, alliance death wreaks untold personal destruction. You have to learn how to recognize when your alliance is in trouble, and then know what to do about it.
Certain types of excuses crop up over and over again in EVE. "We didn't want that anyway" goes in the same bucket as "It was just holding us back," "Now we're really mad," and any reference to wounded tigers.
Read The Mittani's full advice on How to Survive a Failure Cascade.