From a technological point of view, is there any reason this is only possible now? Or would it have been possible decades ago, if only there had been enough interest in it or someone had had the idea earlier?

This seems like a really smart feat of thermodynamical engineering, but it does not reference explicitly any technology that would not have been available 30 years ago. I could imagine that being hidden in the subtitles of getting the process efficient enough - e.g. in computer-based component design and CFD simulations.