Several notable billionaires experienced massive hits to their fortunes Monday as the Chinese generative artificial intelligence startup DeepSeek upended the U.S. stock market, hitting the American AI leader Nvidia the hardest.

The recent AI advances by Chinese upstart DeepSeek could be the beginning of a potential nightmare scenario that Nvidia Corp. Chief Executive Jensen Huang has been worrying about since the chip maker’s meteoric rise.

Nvidia shares' 9% recovery Tuesday was the second-best day in terms of market cap added for any company ever—but the company faced another selloff Wednesday.

One of the biggest beneficiaries of this trend is Nvidia (NASDAQ: NVDA), which pioneered the graphics processing units (GPUs) that have become the gold standard for running AI systems. However, reports emerged recently that suggested a Chinese start-up had cracked the code for developing strong AI systems while using inferior chips and novel training processes.