Well yeah, as noikeee says, most of DTM drivers, including successful ones have gone through various feeder open-wheel series, i.e F3 or something like that. So it doesn't mean F1 drivers are naturally untalented to drive touring cars, I think there is a deeper issue. Let's take a look.
The division of those drivers come after F3/GP2 careers. Some of them make it into F1, either by being truly awesome, having right connections or money. Others don't get into F1. It doesn't mean that they are talentless hacks. I believe the likes of Wittmann (current DTM leader) would do at least a solid job in F1. But they didn't have the right opportunity/connection, so chose the DTM path, because it is a paid job. The former DTM champion di Resta, whatever anyone thinks of him, was in my view at least a solid F1 driver as well.
Then those "non-F1" blokes go to touring/sportscars, including DTM. It means they join DTM at the age of, say, 22. I believe the fundamental difference is that drivers at such age are more adaptable. And those, who join a certain series at the age of 22 are able to get on top of things much quicker than those, who join at 30+. Because F1 veterans usually are already 30+, when they finally get into DTM. We can look it the other way around too. Drivers, who get into F1 at the age of 30+, usually have a hard time succeeding, even if they are talented. It is considered even Bourdais joined F1 "too late", while he was "only" 28. I certainly think Bourdais is more talented than he managed to show in F1. I think Damon Hill was the last driver to truly succeed in F1 by making a late (30+) debut.
So it works both ways. It is just a natural thing of a human being in a sport. If you have got many years of headstart and started doing something at the age of 22 as opposed to 30, it is likely the "old-starters" won't be able to match you any more when they join too.
Edited by sopa, 13 September 2014 - 21:06.