In Germany since the 80s the RPG market has been DSA, a long time nothing, then simply "rest" Pathfinder has taken over D&D's old place (with D&D all but dying out after losing too many grognards - who happened to provide most of DMs and Organizers and then adding insult to injury by having the plug pulled from the German translation which all but killed recruiting of new players to make up for the people having left to Pathfinder). That means second place or from time to time third place if some temporary fad gives some other RPG it's "five minutes of fame". In any case second place means barely seeing the rear lamps of DSA so far ahead.
I really can't nail it down why it's this way, just somehow DSA hits some special German nerve or mentality that makes it so hugely popular in Germany but bombing everywhere else.
I can't speak for anyone else, but I assumed it was in German. Thus it's gonna bomb with anybody who doesn't speak German. I never assumed I would understand the game.
If that perception (that it's in German) is wrong, maybe the bombing issue lies is the international marketing which failed to communicate that fact.