The attraction for him is that he is young and if you want to start over he may be the guy to focus at drafting. Again it's just a perception.
He's into analytics, which Pittsburgh wants to be more involved in. Apparently, they don't have an analytical department, and don't use much in the way of advanced stats.
The new owners own the Red Sox, who tried to steal Billy Beane from Oakland As when he kick started the whole analytics craze in baseball - successfully. They probably view Dubas as hockey's version. Toronto has been an organization deep into advanced stats, including using pNHLe for draft prospects, and with the NHL team itself.
Toronto hasn't had playoff success, but they have had strong regular season teams, and are deep organizationally (Marlies are always good) since he's been G.M.