Chelsea and Spain dominate games, unlike we did (mainly) when Torres was at his best form. Defences drop a lot deeper against Chelsea and there is simply no space for him to run into. Also their wide players are a big feature of their game, which doesn't suit Torres.
In a counter attacking team, at the top of a 4-3-2-1, he will score bags of goals, even now, considering he gets decent enough service. As many others have said, he was a phenomenon, the best striker in the world for a season, he could still score 20 goals a season.
Obviously it's not as simple as I've put it, but it seems only Rafa has found the very best way to utilise him. At Atleti, the whole team was based around him so he was always going to score goals, but he could've got many more than he did, whereas Spain are too good to need to build around him. Interesting to see where he goes from here...