Back to the topic: I think Vine already showed us that there was a market for a video-based social media application that was tied to your @-handle. YouTube has over the years become way too proper and high-effort for creatives that want to do it for fun. Instagram was too picture-based. A good video editor and fame (or notoriety) and the unofficial Vine-descendant is born.
I wonder what the people at Vine thought after they saw TikTok do what they did with a few tweaks.