Their reasoning was MUCH better than that of the government (WHICH GOT RE-ELECTED after their blunder). They disagreed on several government claims that proved to be outright wrong.
Being smarter and having better conclusions than the government is a good trait for experts.

The majority of Europeans was smarter than the Bush team, but since the U.S.Americans don't listen to Europeans they could at least choose their experts wisely.

And contrary your side blow about funding, they spent their own money to warn the public at a time when the media failed in its mission.
That's what's known as civil courage in Germany - to stem your weight against bad actions (including against the government) even when you have reason to worry about your well-being (in this case in the profession) if you do so.
They showed character when the vast majority of think tank talking heads swam with the current into the wrong direction.

THAT is why they proved their value and deserve to be listened to next time they advise the public.

Who wants to bet against me when I assert that Michael O'Hanlon* still gets more time on TV than 80% of the people (if not all) who signed the NYT ad in 2002 together?