There could be a drastic change under way. That's what permabulls don't realize. Until the 2015 lows are broken, it's still officially an uptrend and bulls can cling to that. The trend is your friend until it ends. Of course, there's no guarantee the trend will sustain forever. That's why I think it's important to always take some profit out of the market during bubbles. If Bitcoin fades away and heads back towards $0, it would be a damn shame to be a hodler and give back all your unrealized gains.
We all know that it won't happen, right? Shifting price drastically is a bit too much, we all know that it will go down slowly before it goes back to $0, but $0 is too much just think about it and you will figure it out. It is not just 1 person or group making the fluctuation of the market.
I'm a long term bull, but I'm also a realist. Of course it could happen! Much of Bitcoin's value is grounded in speculation about future usage. If adoption fades away and the market collectively realizes the prospect of mass adoption is dead, the long term bull trend will reverse to a long term bear trend.
I doubt Bitcoin will ever go to zero no matter what, but it could definitely bleed back down to price and volume levels where it's basically irrelevant.