According to the Washington Post:
"U.S. military and
intelligence officials said that Mullah Fazlullah, the mastermind of the
attack on 15-year-old Malala Yousafzai, operates out a region adjoining
Pakistan where several hundred US troops are stationed. But they said
finding Fazlullah is not a priority because he is not affiliated with
al-Qaeda or with insurgents targeting US and Afghan interests.
“Our guys just aren’t tracking him,” a senior Special Operations
official said. “He is viewed as an ‘other-side-of-the-border’ problem.” When
asked if Fazlullah was a priority, a senior intelligence official
responded, “Not with so many other potential targets” in Afghanistan."
Exactly the same way as the Haqqani Network is viewed in Pakistan, as just one of those 'other-side-of-the-border' problems.