in my opinion, this is what happening right now as the trend of bitcoin price has been sky rocketing. what do you think affects the price increase of bitcoin today?
Mostly speculation. People are buying bitcoins and expecting to make money when they sell at a higher price.
And the danger in this is that it works until it doesn't. If the only reason to buy bitcoin is to try and sell it to someone else later at a higher price, eventually one of two things happens: 1) you eventually run out of people to sell to because everyone already owns bitcoin, and with no future people to sell to, the price crashes because nobody can make a profit by holding any more; or 2) people realize that scenario one is inevitable and stop buying before everyone owns bitcoin, because the realization that the only way to make money on it is by selling it to someone else at a higher price is an investment structure that is shaped like a pyramid scheme (albeit unintentionally, but unsustainable nonetheless), and the price crashes.
Either way, it seems a price crash is inevitable because Bitcoin's utility as a speculative asset comes to a definite end, and there isn't now, and likely won't be in the future, enough utility in any other use case to maintain the price.