/r/videos used to be a default and supposedly has millions of subscribers, but when I was still on reddit you'd regularly see content with 100 upvotes reach the top of the subreddit and maybe 10 comments. Often this was on bot reposts.
Their numbers should be take with a huge grain of salt.
The younger generation is less tech savvy than the millenial generation who were forced to figure stuff out themselves and didn't have smartphones.
I get the idea that a lot of people who emigrated to the fediverse are older and also more tech literate given all the linux memes.