The whole point of defense is to stop the other team from scoring- turnovers are obviously part of that but certainly not THE point
There is obviously some skill involved in generating turnovers - ripping and punching the ball, breaking on a route bc you’ve studied tape
But there’s way too much luck involved to bank on turnovers as a core strategy
(knowing where Manning is likely to throw on a route is skill/smarts - being in right place/right time when Favre has a brain fart is luck)