Politicians usually don't know anything about the domains they are put in charge of.

Their role is to provide leadership and direction based on the views of the people they represent.

When dealing with domain specific decisions they should refer to subject matter experts to seek advice and understanding of the available options. The ministries/departments exist to provide that advice and support its implementation.

A ministers job is to use the advice provided by their ministry/department to select a path forward that aligns with the direction the minister has set.

A minister ignoring advice of the ministry/department tells the department the leader doesn't respect or value it. This is really bad leadership.

It also means the minister isn't operating from a position of strength or knowledge. This means your more likely to make poor decisions which move you away from your goal.

I am not saying that aren't wider factors, but you expect the ministry/department to account for that as the minister should explain those.