Why are UK Ministers Manipulated by their Civil Servants?

In the UK political system ministers are appointed by the Prime Minister. Thus ministers are shuffled from department to department without having any expertise in that field.

So you can have a minister of sport who has never played a sport who then becomes a minister of education, despite not going to a comprehensive school and finally perhaps a Foreign Minister when their experience of foreign affairs is limited to 2 weeks in the Bahamas every winter and 2 in Nice every summer.

Of course they will be misled and abused by civil servants who have spent years in their field.

The answer is to appoint ministers according to their field of expertise not their seniority.