If you call bitcoin and other crypto currency stage a bubble, then it has been bubbling up many years now... srsly... The only downside is that crypto currency maina that surrounds this today is that people don't see it as an alternative currencies they see it as a money making machine. Many people still enter the scene just to be able to "cash out" at end but they fail to understand that bitcoin and altcoins are actually money and that there is no need to trade them for fiat currency back again - this in my opinion is why you have swings with high proportions. People rather see it as an asset than as an currency.
It might be a bubble who knows, only time will tell. Tbh I thought many times that bitcoin is entering the bubble stage that I don't really know what to think, easier is just to hold. Because we all could be fooling ourselfs that it isn't bubble, because it wasn't been the case the last time - but on the other hand we all could actually be wrong about the bubble thing as well, maybe just people are starting to take a notice of bitcoin and other crypto currency.
bitcoin bubble is a trick of the media and the elite. Because they are afraid of the bitcoin strength that in the future will acquire fiat currency. Because fooling the community is the task of the media. So for those of you who have bitcoin, please hold it and keep it in your own wallet, we wait in 2020 for further bitcoin development.
This could easily be the case as well, because those people are comfortable, banks haven't had any competition till now so the best way is to try to scare people to not even think about bitcoin, remember "it is used to buy drugs on the internet" you don't want to be flagged as some shady person don't you

I'll leave you with the quote from Gandhi
"First they ignore you, then they laugh at you, then they fight you, then you win."