To provide a more credible and well briefed Foreign Minister, as Boris Johnson clearly lacks the skills profile necessary to be effective in his current role. Importantly he lacks the tact, diplomatic, negotiating and interpersonal skills required for such a pivotal position in government as evidenced by recent pronouncements and radio interviews.
Why is this important?
To allow the government to effectively undertake Brexit negotiations and other important internationally focussed negotiations with friends and allies about Britain's place in a changing world.