Islamist fanatics, as you would expect, are very earnest about their beliefs. They accept that secrecy and deceit are necessary to mislead the enemy, but they do not expect their leaders to be lying to them. When they find out that they have been lied to, consistently and over a long period of time, they get very cross — and this has repercussions in the real world.
From the time that the Taliban conquered Kabul and took over most of Afghanistan in 1996, Mullah Mohammad Omar was the man who ran the show and was effectively the head of state. He was the man who allowed Osama bin Laden to set up camp in Afghanistan. And although the Taliban lost power after the U.S. invasion in 2001, Mullah Omar remained in control of the organization until his death in 2013.
The trouble is that nobody told his faithful followers that he died more than two years ago in Pakistan. Until last month the Taliban was still issuing statements in his name — most recently, on July 15, a message endorsing the Taliban's recent peace talks with the current Afghan government. Now all Mullah Omar's statements since April 2013 are in question, and so are the men who made them in his name.