I think you're exactly right about the "category of systems" thing. If you're "just"[0] moving protobufs across networks, then Go seems like a perfect langauge, esp. if you can just codegen the protobuf code. There's obviously more to it, but that seems to have to been the spark. To be fair, Go does does seem to work quite well for infrastructure code, but in those use cases you're usually just working with very concrete things and are not super-worried about abstracting over "effects" and that sort of thing... because it's all effects and everything is extremely concrete if you're interacting with e.g. the Linux 'container' infrastructure.

[0] Of course, it's never "just".