[1] https://reddithelp.com/hc/en-us/articles/360060476592-Intern...
[2] https://old.reddit.com/r/SubredditDrama/comments/n8g2om/redd...
I think a major problem for this was the limitations of german community. It's seems most are very young with very specific interessts and culture, so naturally they end up with content that caters to just those people, while the rest just hangs out in the better international subs.
But I agree with you and personally spend most of my time on reddit on international subs. But it doesn't make sense for a German to spend much time on r/personalfinance for example because it's too US-centric. That's where r/finanzen (and r/mauerstrassenwetten (like r/wallstreetbets)) is the better place.