From HSToday:

[After the death of Osama bin Laden] Al Qaeda’s franchises were unsure of the leadership credentials of Bin Laden’s natural successor Dr. Ayman Al Zawahiri. While Al Zawahiri was the source of the theological inspiration behind Al Qaeda’s actions, he had little operational experience. The lack of attacks by Al Qaeda in the West since the death of Bin Laden seemed to back up that hypothesis. But what was going on was far more complex. The hierarchical structure that had served Bin Laden so well started to morph into a federated relationship structure. And this was always likely to have its problems as Al Qaeda franchises and jihadi groups vied for position.