I don't think people quite grasp how dire this is, and just what we've now lost.
Robert wasn't just a Community Manager. While other CMs would post on various metas, help in chat, answer mod tickets... Robert (generally) didn't do those things. Robert had a different role, as far as I can tell.
Robert gave life to new communities.
I used to be quite active on Area 51, the new site building site. The software was ancient, and not well-suited to its purpose even when it was new. It was flooded with clueless people who somehow wound up there. And it was where new sites were built.
Robert somehow, for years, made Area 51 work. Whether it was mundane tasks of simply deleting misguided proposals, or the rather more difficult and important task of guiding the building process of a new site, Robert's hand was there. Guiding. Helping. Pushing, when necessary.
He would often lend his voice to discussions on the scope and focus of a site before it launched, raising points that nobody else had thought of. Without him, many of the sites we currently have would not have made it past the "follow" stage on A51.
And then, after the site was launched, Robert would come along as well. He would guide the brand new site, moderate it, direct users, and help shape the site. Many of the things that I would learn about building a new site came directly from the advice Robert gave me and others when building such sites as Artificial Intelligence, Interpersonal Skills, Literature, Constructed Languages...
Without Robert's guiding hand, Interpersonal Skills would have collapsed in a week. Literature would have gone in a totally different direction. There are countless other such examples.
Robert was also dedicated to making improvements to the sites that may have seemed small but would have massive effects. Whenever he did weigh in here on Meta.SE, his ideas and voice were always eminently reasonable - a talent born of the experience of years of working with the system and the people.
It's this experience and guidance that we've now lost. It's a devastating blow.
Thank you, Robert, for everything you've done over the years. It's been a pleasure.