Isn't investment like a form of debt, or well obligation to make returns?

If VC provide you funds, there is an expectation of returns, otherwise the board would vote you out.

Yeah it's not a traditional loan from a bank, but it's not a 0% interest loan either.

The duopoly AI labs haven't technically borrowed much, but a metric ass-ton of money has been borrowed by various other entities in service of them as infrastructure proxies.

That's what is driving up the cost of debt and teetering some of these companies into junk status.