There is a lot of speculation why ex-Prime Minister Jamali was ousted. The different people are expressing different opinions in the press.
Our president has been rendering a lot of service to the United States of America in the aftermath of September 11,2002: let it be war on terror or aiding USA in its war in Afghanistan and in this process has purchased enmity of a cross section of the people in and outside the country resulting in three attempts on his life. Thank God he has escaped unhurt.
Another political upheaval is also expected by the close of the year on the issue of the president relinquishing his "uniform".
The benefactor- USA- may, therefore, have realised the gravity of the situation and felt it necessary to plant yet another man of its confidence in the shape of Shaukat Aziz with a view to ensuring continuity of service required of Pakistan in pursuance of its global policy even if the President leaves the political scene, chances whereof seem rather far-fetched at the present.
Thus plantation of Shaukat Aziz is rather a "pre-emptive attack" by USA to safeguard its future interests in the region.