The problem of seeing a bubble from the inside is that all the data is solid: you know people who trust the currency, every time there is more, all are indicators upwards ... it is very difficult to leave this small world and look in perspective what's happening.
The first bubble known or accurately described by the history books was that of tulips in the Netherlands. Although they arrived in Europe in the 16th century, it was not until the 17th century that they became fashionable. And they went up in price, a lot and very fast. What was a decorative plant became a good business, since they could be bought and resold later for more money. That is, people began to speculate with them. The tulips are pretty, nothing like that existed until then and there was a solid demand. What could go wrong? The problem is that they really do not work at all (more than to decorate) and when people finally realize it, prices plummet.
Something similar happens with Bitcoin. Although it is a scarce commodity, it is useless. It has no legal tender, there are hardly any businesses that accept it (except illegal and some business that wants to advertise even though it is impossible to fix a price in Bitcoin due to high volatility) and its value is based strictly on the trust of its users.
In addition, the rise we are seeing is based solely on the arrival of more and more capital. That is, Bitcoin's purchase and sale volume is increasing, as in all bubbles. That's why the price goes up. New capital arrives above the rate of creation of new Bitcoin (it is a well designed to be scarce).
Therefore, when the music stops, when people realize that they are putting money, a lot of real money into something that is useless, the bubble will explode. The price will sink, the volume will be reduced.
This is, basically, what the CEO of JP Morgan said a few days ago, and he has been criticized for doing so since he is an interested party (since Bitcoin could be an alternative financial system to the current one). And so it is. But you have to remember that even in the biggest bubbles, like real estate, there was an underlying underneath that was worth something. In this case Bitcoin is useless. It is very dangerous to put money there.
Some would say to me: listen, because this is like gold, it is useless and has a value. It is true. The utility that gold has in the industry is marginal compared to the use that is given in jewelry or simply to store wealth. But there is a big tradition, centuries of history. Not here and therefore the house of cards is more fragile.
"When will the bubble burst?" I do not know. Nobody can know. But as they say the stories of the crisis of 29, when everyone talks about a financial issue without having a clue is a good sign that you have to sell. On that occasion, shoe cleaners were talking about actions. Now it's people who do not follow the economy closely talking about Bitcoin and recently I've experienced it.
Also, Bitcoin is "bubbling" for 9 years already. If you check other bubbles and crisis in the last few decades, you can check it would burst about 5 years ago, if not more.
Oh, and the Tulip mania isn't "accurately described by the history books". Inflation and natives slaughter in the Americas were the most determinant aspects that led to the whole thing. It wasn't even about the speculation.