At the time the newly-installed civilian government was trying to take firmer control of the ISI. That would have involved dismissing or at least reorganizing personnel. The Mumbai attacks created a situation where war with India was portrayed as imminent. I'm sure that had the effect of halting ISI reform in its tracks, at least for a while. That, I think, was the purpose of the Mumbai attacks.
(An alternate story that started making the rounds of the D.C. rumor mill last year was that it did indeed start out as an ISI operation but degenerated into a terror attack on civilians once the reigns were given to the LeT leadership. I don't put much faith in it, but it does have the advantage of providing sufficient "cover" so Pakistani officials can still be invited to diplomatic receptions.)
All of this is, as you yourself pointed out, rumor mongering, not unlike the 'CIA and/or Mossad did 911' rumors out there.
If you don't think that Pakistani bureaucrats would stoop to murdering innocent Indians just to keep their jobs, then I think you don't know the history of Pakistan very well. How many times was there a coup, or nullified election, or extended war because somebody didn't want to step down from power? A lot. This act may have been carried out in the same spirit.
The only 'murderer of innocents' that I can think off is Zia-ul-Haq, who hung Bhutto.
Aside from that the wars that have taken place were not initiated by a particular individual/entity/institution because he/she/it/they wanted to retain power or capture it.
1947, a tribal invasion launched because of the Maharajah's persecution of Kashmiris fighting against dictatorship not sparked by an intra-Pakistan power struggle.
1965, a war after a Pakistani covert bid to instigate a rebellion against Indian occupation failed, not sparked by an intra-Pakistan power struggle.
1971, a war after successful covert Indian support for rebels/terrorists in East Pakistan, and mismanagement of East Pakistan affairs by the GoP.
1984, Siachen conflict initiated by Indian occupation of glacier.
1999, Kargil conflict initiated by Pakistani occupation of Kargil heights - power struggle arose because of the Kargil conflict, the conflict was not the result of a power struggle.
So I think it is pretty clear that your arguments calling Pakistani leaders bloodthirsty and capable of terrorism and starting wars for the sake of war have absolutely no basis, and your entire analysis is delusional.
Perhaps the most amazing thing about America has been the willingness of its leaders to leave power - and the refusal of the populace to contemplate anything other than the law of the land for the succession of power. It is a test of both country and character.
Agreed to a degree there.