I know byte just released, but as someone who has used TikTok for a few months now, the difference is honestly night and day.
- byte sticks to the very strict 7s limit while TikTok is a bit loser
- TikTok's use of music and re-used sounds help bring popular "trends"
- As per the above, you can quickly browse other tiktok's made from the same sound / in the given trend
- TikTok has other interesting features too such as duos, letting you reply to someone else's video, side-by-side
- TikTok's are very easy to share, and most importantly have a Web UI
- TikTok doesn't require an account, as soon as you open the app, you're dropped right into a feed of interesting videos, easy to scroll
These platforms are all about content, and TikTok having penetrated the US means it'll be very hard for byte to get users, and without users there's no content.
I personally don't think Vine really failed per-se. Twitter just didn't think it was a place worth investing, so they stagnated. TikTok as mentioned above has brought many new interesting evolutions to the format.
Most importantly, their learning based feed is pretty top notch and learns your taste very quickly.