Those digital asset trends are "100% based on greater fool theory," the  Microsoft co-founder said Tuesday at a TechCrunch conference 

Gates added that he's "not long or short" crypto. And he mocked Bored Apes NFTs, joking that "expensive digital images of monkeys" will "improve the world immensely."

Instead, Gates said he prefers old fashioned investing.  "I'm used to asset classes, like a farm where they have output, or like a company where they make products," he said.

His comments come as bitcoin and other cryptocurrencies are crashing. Bitcoin hit an all-time high of $69,000 in November 2021. 

Since then, the world's most valuable cryptocurrency has lost two-thirds  of its value, tumbling below $23,000 on Tuesday. It has lost about 25%  of its value since Friday. 

Crypto exchange Coinbase announced that it's laying off 18% of its  employees as the digital currency market continues to crumble.  

Gates has previously doubted crypto. In a 2021 interview with Bloomberg,  Gates said that it was one thing for Elon Musk and Tesla to invest in  bitcoin, but that doesn't mean average investors should follow that  lead. 

"I do think people get bought into these manias, who may not have as  much money to spare," Gates said. "So I'm not bullish on bitcoin."