Busy servers generate more heat. Inefficient code makes servers busier. There’s a real physical outcome for bad performance code at scale.

But you don’t really want lots of idle or underused servers, aside from burst capacity management. So if they universally and consistently wrote more efficient code I’d expect a smaller datacenter. Full of still busy servers but just less of them.

He was showing how complex and expensive a data center is and giving them real-world visceral experience that inefficient code has real-world implications.

Maybe he got PTSD from being a former tour guide and this was his time for vengeance.