I think the coordinated articles in the Army Times, The Air Force Times, The Navy Times, and The Marine Corps Times was the proverbial nail in his coffin. The election did not help either.
I think the Bushies are trying to show the American people that if you clean the window the items on display behind the window will look prettier, even if it is an ugly deceit-laden profiteering war with no end in sight. (see the Bechtel withdrawal from Iraq for more details)
It is interesting to note the number of high-ranking military that have publicly criticized Rummy. After re-reading ‘Plan of Attack” though, Rummy ignored the military background and expertise of his underlings when it came to war preparations. Franks wanted something like 300,000 men on the ground, which Rummy kept whittling down.
The Abu Ghraib and Gitmo abuses refelcted very poorly on his leadership, and I am not so sure he ordered abuses like some claim, but it is clear that in the very least chose to ignore the abuses after he became aware of them.
I do not know if it will ever materialize, but there are suits being pushed forward for prosecuting Rummy on War Crimes charges, so he might have to face a jury.
In a previous post, I argued it would not matter if he were replaced. It is the bellicose policy that is flawed. We will see if his replacement heeds the advice of those around him better than Rummy did, but I am skeptical.