You made a very important observation; snapchat’s design is confusing to some because it breaks traditional metaphors and conventions for app design. Hence it is confusing to those who are expecting those conventions. But to those who do not come in with any expectations about “how an app should work”, it isn’t confusing at all. In fact, it is MORE intuitive because it takes a fresh look at UI from first principles, rather than starting with established metaphor. And because it is more intuitive, it rewards those who use the app heavily.
This is why Snapchat found an initial user base with teens; those with the least expectation for what UI “should” look like, and those who use it the most.
The UI (“unfolded cube” vs “hamburger drop down”) is only one way that Snapchat brings a fresh view to the overall product UX. Another example is Stories, which are told in chronological order. The convention for social network “feeds” has been reverse chronological order since Friendster and for no particularly good reason. Yet stories are told “beginning — middle — end” not “end — middle — beginning”. Such an obvious observation in hindsight, yet Snapchat was the first to build a product that way.
Video Chat is another great example. Video calls have followed the phone call metaphor from the beginning. FaceTime “rings” and you “answer the call”. But this is all a holdover from the times when you didn’t know if the other person was there to pick up the phone. Snapchat’s video Chat is integrated into Chat, and if you’re messaging someone, then by definition you know that they are there. So it doesn’t need to ring, it can just start. And it doesn’t need to be two way video by default either. Again, obvious in hindsight, but snapchat was the first to build a product that way because everyone else’s thinking was constrained by conventional UI metaphors.
One such observation might be a lucky accident. This many starts looking like a pattern, and that is competitive advantage.