Or they thought that America will keep on funding them for their services and Afghanistan will remain a state under their will. Not much happened in favor of Pakistan because Taliban established links with their mentors particularly with other American channels and became almost independent of Pakistani influence. Pakistan in return has repeatedly told the Americans that they should directly contact Taliban. And that is where truth lies because Pakistan, though a little bit late, has come to know the other links of Americans and Taliban. By terrorist activities American mean only targeting Osama Bin Laden and the rest is fine with them.
Answers lie in the overall game plan that America has for the region since decades.
After the withdrawal of Russians from Afghanistan, situation could have returned to normalcy, had America or Pakistan, Iran and Central Asian States wished so because all of them could influence their sponsored groups to sit on negotiating table and form a moderate government, which could be friendly to the Afghans and to the regional countries. However, that was not done and instead Taliban were launched successfully to avert any possibility of formation of a liberal government. This simply means that Americans want to keep the region turbulent and volatile so that a regional bloc comprising of Afghanistan, China, Iran, India, Pakistan, Central Asian states and Russia is not formed. And in this regard even a fraction of ever lasting peace coming to the region will not be tolerated. Americans are true to their national interests because one can imagine if it happens that way and regional block is formed or peace returns to an area stretching from Bengal to Baltic Sea, then the monopoly of America would reduce to only one third of planet earth.