Yes, Pakistan could control those radical Islamists if they have not being given the weapons and other equipment from outside sources. I couldn't say what sources since I am not absolutely sure about that, and I don't have the evidence, but what is evident is that they are being empowered by some powerful outside organizations.
The radical Islamists continue to grow in strength and in numbers. They have proven to be difficult to control and quite fearless. The Pakistan forces can't stand up to the force the radical Islamists bring by themselves. The only way the group can be handled is if they are stopped by multiple nations coming together.
Pakistan can not control radical Islamists. Nobody can, no country can without the actual political will to do so. Trying to accept it, reframe Islam as some peaceful religion, or trying to be nice to them will not work. The only thing that will work is its total and complete destruction. Good luck with that.
It is next to impossible for any country to control radical Islam. The only way to even come close is to stop immigration of Muslims and deport all Muslims in a country. This action alone is questionable and next to impossible in itself. Actions by a small group of individuals is more difficult to predict and prevent.