They were the first ones to do it at scale. Before, you had to seek out the debauchery. TikTok is saying, don’t worry, we have hundreds of scrollable hours waiting for you, just keep scrolling.
Vine had no where near as good of a recommendation algorithm as TikTok. Reddit for over a decade relied on self-curation and upvoting to determine what to show you.
TikTok curated content without the need for a user to do anything else than scroll. You can have a remarkably well personalized TikTok experience without liking, following, or saving any content.