Go was chosen mainly because it aligned more with how the existing compiler is designed. They did not want to redesign the compiler which eliminated C# as a choice. So Go is apparently just a better fit for quickly porting JavaScript code to.

That was the original motivation yes, although they acknowledged later that the weaker type system from Go required redesigning the data structures anyway.

And as proven in the recent announcement, they had to rewrite parcel from C++ into Go, as they didn't found a comparable library in Go ecosystem.

There is also another interview, where again they mention having used AI as tool for code rewriting as well.

Also to note that it was pointed out that Native AOT wasn't up to the job, again something that both Java and C# failed not having done it properly from day one.