I think it's super fascinating and unexpected to have passed "met through friends" which I would have guessed would still be a strong mechanism. I definitely find the relationships I've started with friends of friends were always stronger and lasted longer due to the social momentum and both having more "skin in the game" than ones I started with random people from online. The biggest problem is the friends of friends pool is far more fixed and people tend to be hesitant to introduce people at the risk of creating possible conflicts within friend groups. The online line shooting up is sad because I feel like my experience on the common dating apps has only gotten worse over time. That may also be attributable to me just getting older too confoundingly.
I seems especially puzzling that "met in a bar or restaurant" is the only other (non-online) response that trends upward post-2000. Why would that be the case? It almost makes me wonder whether "we met in a bar" is a common response from people who are embarrassed to say they met online...