Snap is not a clear case of failing. Sure, they did not displace Facebook, but the founders and investors made a lot of money and while it isn't growing as fast as it should, it is still growing every day.
Simple. Either revenue/profit or growth. That's all there is.
If your business model is network based, you can go for "grow now, monetize later" model. Then you need growth even if it means revenue sacrifice.
If your business model is not network based, then revenue/profit.
In case of Snapchat, they made personal gains for the founders and the VCs, but from company point of view, they don't make no money, their growth has stalled. The industry #1 has exactly the same app with larger user base and faster growth.
I can't think of a single reason why this would fall into a success category. If anything, the founders and VCs cashing out so much when the company is dying indicates failure rather than success.