1. Content that is profitable from an advertising perspective
2. Censoring certain content/only showing major/authoritative sources.
TikTok changed that by allowing grass roots content to go viral, which from an algorithmic perspective is less profitable. But that doesnt matter, its backed by the CCP. Theres alot that goes into why tiktok is better, and alot of it is monetary/business related, not computer science.
But beyond that, FB/Google just got lazy and stopped pushing for new things. Wildly successful and presumed monopolies, they left a massive product gap (allowing grass roots content to go viral), which TikTok filled.
They hype around it is because it is the current thing.
[0] https://futurism.com/tiktok-spy-locations-specific-americans
Heck, a big part of TikTok was Musical.ly, an app for lip syncing videos. That was a huge stroke of luck/foresight because it gave TikTok a lot of the music rights deals they would need to allow people to put videos to music.
Are you really arguing an app around individual videos set to music (which, in my experience, is still the vast majority of TikTok videos) is somehow an "incremental product change" to a friends-based social network?