*Why* did Zaarin defect?

[Illuminatus Primus]

The idea is simple: Like ancient Rome, Zaarin was an influencial and powerful military leader and believe such would guarrentee him dominance. Because of the Rebels latent support, their success with the Death Star I's destruction, and the neccessity of holding down every single sector with dozens of Star Destroyers, he believed there was significant displeasure with Palpatine's rule on the part of the average Galactic inhabitant. Moreover, agreeing with my theory he was a Grand Admiral, the Grand Admirals wheeled and dealed in the politics of the Imperial court and were considered Imperial nobility. He likely had amassed considerable political assets and spies within Palpatine's heirarchy. A quick strike to the head of the Empire. His supporters would sieze the Palace, and the stunned Empire would except the well-supported military genius (all the Grand Admirals were genii according to the Essential Chronology) and be crowned Emperor in replacement of Palpatine. Unfortunately (for him) he underestimated the skill, genius, and cunning of Palpatine, and the power the Dark Side of the Force bestows on the Dark Lords of the Sith.

[Illuminatus Primus]

Imperial Flight Officer after saving Emperor wrote:
We can only guess at what provoked Zaarin to attempt his coup d'etat.

Imperial fanatic. Unable to grasp how/why anyone would think about overthrowing the Empire.

Mike makes a similar description of Obi-Wan's fanatical brainwashing evident in his devotion to the Jedi Order in how long it takes him to figure out that because a planet is missing from a database supposed to include all planets, someone obviously deleted it. Same fanaticism. It's likely much of the corrupt PT-era Jedi's propoganda and deception to solidify its supposed moral authority when its obviously corrupted.

The New Jedi Order and the Ancient Jedi Orders are what the Jedi were intended to be. The Old Jedi Order (PT-era) was so corrupt and distorted it deserved to be destroyed.