No doubt, this is a strategic move, as the article speculates as well. No mafioso hands himself in. It's weak and dishonorable.
And believe me, when they're on the run for so many years, they're almost (almost) relieved when caught. Nothing is better than freedom, but it takes it's toll on you after so many years in hiding.

The reason you see them smiling, is because these are the fugitives and their families are always there to "greet" them and wish them well. They are smiling over to their families.

As far as the Italian judicial system, don't forget there is no jury. Judge hands down the conviction and the sentence. Done.