Earlier quoted context omitted.
It's a good point, after so long why the JVM is not written in Java actually? For example the Go runtime and I think C# as well are written in their respective language. https://github.com/golang/go/tree/master/src/runtime https://github.com/dotnet/runtime
Java isn't as performant as C++. BTW, how do you implement a garbage collector with a garbage-collected language?
You write it carefully so the garbage collector itself doesn't also need to allocate objects.
Here's a GC for Java written in Java https://github.com/oracle/graal/tree/master/substratevm/src/....