Nvidia's blowout earnings are hiding a growing risk that could eventually crash the stock — good for holders now, dangerous later.

• Sales jumped more than 70%, far past what Wall Street expected, and margins are still huge.
• Half of Nvidia's revenue comes from just four customers, so even a small cut in orders would gut growth.
• Nvidia is also lending to and taking stakes in the AI companies that buy its chips, turning it into a kind of bank with exposure to shaky borrowers.
• The setup looks like Cisco in 1999 — profitable, dominant, selling the picks and shovels, and quietly investing in hundreds of the startups it supplied — before its stock fell 95%.
• Private credit is already cracking at firms like Blackstone and Blue Owl, a warning that the credit cycle is turning.

Outlook: The stock likely runs higher over the next year, possibly past $350, but a turn in the credit cycle could take it most of the way back to where it started.