A ROK Drop favorite BR Myers gives his analysis on the Jang Song-taek purge in the New Republic. I agree with his analysis that this was not an ideological battle because the regime elite understand the importance of the ‘Myth of Kim’:
The Western reaction to it has been predictable enough. Americans cannot shake the mirror-imaging notion that the North Korean elite is divided into reformers and hardliners. It seems any official involved in trade is considered a reformer, while anyone in the army is a hardliner—especially if he took part in one of the two attacks on South Korea in 2010. It’s not even good mirror-imaging. Was Colin Powell the hardliner in the Bush administration? Is a US general in Afghanistan more hardline than a general at Fort Bragg? In fact the North Korean military is involved heavily in trade, and its fighting power is enhanced by the revenues. It arguably has as great a stake in economic change as anyone. Yes, you have bitter institutional rivalry in Pyongyang, but that does not mean ideological disagreement. The South Korean experts seem to get this; they know how Korean organizations work. [New Republic]
You can read the rest at the link but Dr. Myers seems to agree with my analysis that Jang was purged as part of a competition for regime resources. I think Jang was trying to rebalance power in the country between the military, party, and government bureaucracy. The military has their own moneymaking schemes and Jang may have been intruding in these schemes and funneling money to the party and government.