THE CALLING OF NEW APOSTLES
See https://deseretnews.com/dn/view/0,1249,595081177,00.html
The death of two members of the Quorum of the Twelve of The Church of Jesus
Christ of Latter-day Saints within the past 10 days is not only
unprecedented in recent Church history but creates vacancies in the group.
This article describes the process for calling and ordaining new members of
the Quorum of the Twelve Apostles.
The calling of a new Apostle is done through revelation. However, God does not select who he wants as the next apostle, then tell the Prophet. It is done the other way around. The Prophet, and or the surviving Quorum members make the selection then approach God in prayer for a confirmation. That is why most of the senior church leaders are from the Western United States and many are related, either by blood or marriage. Since those submitting the candidates to God are only going to consider someone they know, the Quorum will consist of men who are known to the Bretheren, possibly have worked closely with them and related. Not to say a brother somewhere in Africa might not be just as qualified, but he is not as likely to be known by the church leaders.
The same condition exists at the local level. Bishops are called because they are known well by the Stake President. There may be other men qualified to lead a ward but he may not be someone known by the SP.