> I wonder what the people at Vine thought after they saw TikTok do what they did with a few tweaks.

Well, the founders made ~$10MM each with 5 months of work. So they were probably happy at the time. But Vine was too early, so I think video storage and movement was still pretty expensive for non-FANG companies. So they limited uploads to 6 seconds. I think that limitation was too low to do what TikTok does.

But the real reason they were too early is recommendation systems like TikTok uses seem to have been based on work done since Vine was shuttered.