I'd also like to highlight religious extremism is a problem in Pakistan and
@Rusty2 is not wrong about that, but I disagree the reason behind it is due to Pakistan being an Islamic Republic. And the solution to this is not secularism either but rather state regulation and control.
The reasons behind the extremism can be linked more due to the events which took place in Afghanistan which radicalised large parts of our population, both during the Soviets and after 9-11.
Pakistan has always had a moderate Islamic approach historically, and the extremism you can place on the tribal belt is due to tribal culture more than Islam itself. Hence it doesn't spread that far out.