I don’t know if +Desmond Tutu was ever considered, I am not sure why he would be. The Archbishop of Canterbury is not like a Pope, he is the spiritual leader of the English church. He cannot extend his authority beyond England (and Wales) and the office wouldn’t ordinarily be on the career path of non-English clerics. The Archbishop of Canterbury is selected by the State upon nominations of the English church or Parliament (I forget which exactly).
It is highly unlikely that a foreigner would be considered unless that person had been working in the English church.
Archbishop John Sentamu (born in Uganda) was made Archbishop of York by government appointment but he served the English church for years in pastoral work, so I guess one could say he was ‘incardinated’ into the English church long before.
Bishop Michael Nazir-Ali was born and raised in Pakistan. He also spent many years in the English church and was a candidate, along with Rowan Williams, for the post of Archbishop of Canterbury.
Prime Minister Tony Blair picked the more liberal +Williams for the post instead, which is ironic since Blair became a Catholic later, and yet stuck the Anglicans with someone who cannot seem to forcefully stand for traditional Christianity. It almost seems like an act of sabotage.
Archbishop Desmund Tutu is far more liberal, in a religious sense, than almost any other African bishop. He is far more liberal than Archbishop Rowan Williams if I have read him right.