The success for Go was in the out of the box libraries, and by this I mean you didn't have to "pip install" , "npm install", "nuget install" - no idea what the command is for nuget, always used the GUI, but you get the idea... For example when I was trying to learn Go for the first time I saw how easy it is to dive into Web Development. I can just import a package that came with Go itself, and I would be good. I think also the way it pulls in packages is part of it's success as well. It's not a traditional package manager (yet) but it worked. You put in a repository from the web and it pulls it, it made sharing and reusing code really easy. I never had issues just running Go code either if it was a codebase that was full of mostly Go code.

Btw I don't consider myself a Go developer, at work I use C# and Python. I would love to learn Rust, used to be the other way around, but I've lost hope in Go and have taken a second look at Rust, I love the direction Rust is going overall, but I understand why Go got so popular so quickly, it came at the right time with the right amount of working parts.