PALO ALTO, Calif. — Last year around this time, a toy called a cryptokitty sold for $170,000. A real estate agent remade himself as CoinDaddy, producing cryptocurrency-themed music videos. The man behind a company called Ripple became for a moment richer than Mark Zuckerberg. Kids barely out of high school were buying Lamborghinis because of a crypto meme. Experts went on CNBC to say Bitcoin was going to reach $100,000 per coin.

For a few sweet months of 2018, all of Silicon Valley was wrapped up in frenzied easy money and a fantasy of remaking the world order with cryptocurrencies and a related technology called the blockchain. A flood of joy hit the Bay Area. The New York Times ran with the trend in an article with the headline “Everyone Is Getting Hilariously Rich and You’re Not.” It was temporarily true.

And just as the American public had been given every possible blockchain explainer that could be written, the whole thing collapsed. The bubble popped.

Today the price of Bitcoin — $19,783 last December — is $3,810. Litecoin was $366 a coin; it’s now $30. Ethereum was $1,400 in January; today it’s $130.