What does the 'ad network and search engine' have to do with it? Wouldn't any organization who serves lots of traffic have the same cost cutting goals you mentioned?
Other companies like Yahoo, Whatsapp, Netflix also followed interesting patterns of using strong understanding of how to be efficient on cheap hardware. Notably those three all were FreeBSD users at least in their early days.
Anyways digging it up, looks like the primary author was at Facebook for a year before cgroupsv2, redhat for three years before that, and Google before that. So... I don't know haha you'd have to ask him.