A company that has revenues and is extremely well-capitalized gets debt finance. That is not news. That is totally commonplace. "Shouldn't all their capital come from investors?" No. Companies at all stages typically use a mixture of debt and equity finance.
His EV calculation is completely flawed also. Debt finance is typically senior to equity in recovery at bankruptcy, so when JPMC do this analysis (and believe me they did this analysis) they are not assuming 0% recovery. They are thinking it is most likely in a bankruptcy that they get some x>0% recovery.
Finally, banks don't think about their relationship with a multi-billion-dollar company in terms of the ROI on a single revolving credit. (even though this will in all likelihood be very profitable for JPMC). They think about how giving this revolving credit makes it more likely they get advisory on any future bond issuance and I-banking work when OpenAI want to do takeovers, and a foot in the door at IPO time etc.