The movie is 156 minutes. The video clip is 4 minutes. So that is less than 2.6% of the movie.
PLUS, it is not using the original captions.
PLUS, it is presented in a much lower resolution than the actual move, DVD or Blu-ray offerings.
That makes the content much less that 2.6% of the movie.
No money is being made off of that clip.
The movie came out September 16, 2004. The first parody clip came out August 10, 2006. I suspect that the onslaught of parody clips has increase the demand for rental and purchase of the original movie. I don't think the movie company will be able to prove economic harm. In fact, it should be feasible to prove they obtained an economic benefit. Many parody clips have had comments asking what the move is and where they can get it.
That said, a good deal of the humor involved in the downfall parody clip is in how it mocks the use of subtitles for foreign audiences. As far as non-german speakers are concerned, they could be saying anything. It would be nowhere near as funny if the clips had simply edited out the original audio.
The EFF lawyer stated
All the ones that I've seen are very strong fair use cases and so they're not infringing, and they shouldn't be taken down.
http://www.eff.org/press/mentions/2010/4/23While I suspect the EFF lawyer has not seen this particular clip, it would be fair to expect that the EFF lawyer has seen a number of downfall parody clips that follow this same formula.