Go might have had less marketing than Java, but it still had a decent amount of support. There were several high quality promotional videos when it was first released. The web page is really full-featured; it has a ton of documentation, including translations for several languages. And all those appearances at tech conferences take time & money (and I'm sure that Google sponsorship helped to secure some of them).

All that stuff adds up in terms of manpower and budget, and it's out of reach of what a small independent team can do. It's not all about technical merit.