Because he is Ferguson Mark II - they want someone to continue what has been done, not someone who would do anything different. If he is world-class, why has no other top-team come in for him.
Ferguson Mark 2 - the ultimate insult.
Arguably, the world's biggest club have appointed him, on the say so of, arguably the world's best manager.
They appointed him because they regard him as the best available manager.
Sadly how good he is will be obvious by how fast Everton plummet down the table.