PiS are making mistakes
Only those who do nothing make no mistakes. I do not set PiS policy and am not privy to all the facts and circumstances of the ruling body politic. There are usually reasons for everything. Sacking someone might seem so easy and starightforward to a dilletante or wannabe observing things from afar, but such a move might hypothetically pose a security or other threat to the country or entail some other crucial counterproductive element. Such a one, for insatnce, might be in possession of super-sensitive classified information, to cite but one possibility. Ruling a country is a trifle different from little boys playing with their toy soldiers.