Its called genralization. Whenever a media reaches a larger audience, that media stops filling its niche and starts trying to appeal to the larger audience. Its a bit more complicated when it comes to a social media, but look at some of the larger subreddits. When they were small and starting off, they were fun and exciting. But after growing a larger audience, they became more genralized. A bit boring.

Users are the same way. After a platform gains enough users, those users start to act in a way that is similar to picking the low hanging fruit. Whatever is the easiest way to garner attention, they do it.

If lemmy grows to reddits size, it'll probably be the same. However, hopefully different instances and nonsummarized karma will mitigate that.