TikTok was the first to build an algorithm that created a very comprehensive social graph of your watching behavior. It went much further than even Facebook at the time. Following accounts stopped mattering and it was the personalized feed that hooked people. Hence why TikTok became much more addicting than Vine. Also Vine culture is just very different. It was only a few type of videos that went viral. Therefore it only attracted a specific type of audience while TikTok has a much broader appeal.