Containers happened because running an ad network and search engine means serving a lot of traffic for as little cost as possible, and part of keeping the cost down is bin packing workloads onto homogeneous hardware as efficiently as possible.
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?
Yes, to expand: Both search and ads mean serving immense amounts of traffic and users while earning tiny amounts of revenue per unit of each. The dominant mid-90s model of buying racks of Sun and NetApp gear, writing big checks to Oracle, etc, would have been too expensive for Google. Instead they made a big investment in Linux running on large quantities of commodity x86 PC hardware, and building software on top of that to get the most out of it. That means things like combining workloads with different profiles onto the same servers, and cgroups kind of falls out of that.
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.
It is the unfortunate reality that we tend to only remember the creator(s) of the first version (if anyone). Not just cgroups, but a lot of tech or protocols.
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.
https://en.wikipedia.org/wiki/Cgroups
(arguably FreeBSD jails and various mainframe operating systems preceded Linux containers but not by that name)