I don't think you have done your research yet on what the Ghana Football Federation has seen in him to appoint him as coach, but I have, and I think it is based on the level of experience he has as assistant coach to Alex Ferguson, and won the Premier League and Champions League. He has also been at the World Cup before with countries like Iran, South Africa, and even Portugal.
Sometimes such experience cannot be overlooked. Since he has been in the World Cup before, he understands the tension.
Carlos Queiroz has always been a good assistant manager; I don’t understand why he never quite made it as a head coach. He has excellent tactical knowledge, but perhaps the fact that he never played football is holding him back. Ghana have made a great signing, and I think this will be his last managerial role given his age, but he will certainly give it his all.