Go is a reasonably performant language that makes it pretty straightforward to write reliable, highly concurrent services that don't rely on heavy multithreading - all thanks to the goroutine model.
There really was no other reasonably popular, static, compiled language around when Google came out.
And there still barely is - the only real competitor that sits in a similar space is Java with the new virtual threads.
Languages with async/await promise something similar, but in practice are burdened with a lot of complexity (avoiding blocking in async tasks, function colouring, ...)
I'm not counting Erlang here, because it is a very different type of language...
So I'd say Go is popular despite the myriad of shortcomings, thanks to goroutines and the Google project street cred.
The change from Java 8 to 25 is night and day. And the future looks bright. Java is slowly bringing in more language features that make it quite ergonomic to work with.
I have no desire to go back to Java no matter how much the language has evolved.
For me C# has filled the void of Java in enterprise/gaming environments.
It's fast enough, easy enough (being very similar now to TypeScript), versatile enough, well-documented (so LLMs do a great job), broad and well-maintained first party libraries, and the team has over time really focused on improving terseness of the language (pattern matching and switch expressions are really one thing I miss a lot when switching between C# and TS).
EF Core is also easily one of the best ORMs: super mature, stable, well-documented, performant, easy to use, and expressive. Having been in the Node ecosystem for the past year, there's really no comparison for building fast with less papercuts (Prisma, Drizzle, etc. all abound with papercuts).
It's too bad that it seems that many folks I've chatted with have a bad taste from .NET Framework (legacy, Windows only) and may have previously worked in C# when it was Windows only and never gave it another look.
It was actually really good for the time and lightyears ahead of whatever Flash was doing.
But people rather used all kinds of hacks to get Flash working on Linux and OSX rather than use Moonlight.