It really does seem like a lot of the magic here is simply the format. The video lengths are a perfect balance between short enough to be addictive, and long enough to enable content more varied and interesting than just short gags.

Instagram and Facebook get bland real quick. Youtube/Netflix videos are often too long to be really addictive - "just one more" isn't as persuasive if "one more" takes 10 min+. With shorter skits like Key & Peele on Youtube you do get a stronger sense of that addictiveness. Twitter is mostly text and much less expressive, and even influencers treat it mostly as a communication/announcement platform, not a content platform.

Vine was hugely popular when it was shut down by Twitter, and I think it'll go down in history as one of the largest corporate mistakes every made. They were so close on the format - they just needed to allow slightly longer videos (which they did with Twitter message lengths around they same time they shut down Vine!!!).

I'm sure Bytedance's secret recommendation sauce is good, but I think much of their success is simply thanks to them being the first competent executor of the next major social media content format.