I don't think tech itself is the big employer here in a failure case. Its all the stuff that feeds into the data center build out like construction, electric specialists, all the semiconductor manufacturers, etc. If all those people go out of work at once and there's no other work to pick up the slack, then that could be the unemployment spike that snaps aggregate demand down and starts a recession. When people talk about "too big to fail" this is one of the concerns that makes an industry or company "too big to fail". I don't know if the point of AI is cost savings but in that case we're talking about a technology induced deflationary spiral not a failure of the CapEx spend.

Why aren't tech companies using their mountains of cash to pay for the build out? Why are they borrowing money through Special Purpose Vehicles? Because they want someone else to share in the risk if the build out doesn't work. The SPV allows them to pay a fixed amount for the privilege of off loading some of the risk. I agree that they are obfuscating risk here in a dangerous way but my broader point was that, on its face, this debt load does not have the sort of pernicious systemic failure that makes downturns into deep recessions.