Go was created because Rob Pike hates C++, notice Plan 9 and Inferno don't have C++ compilers, even though C++ was born on UNIX at Bell Labs.

As for compilation times, yes that is an issue, they could have switched to Java as other Google departments were doing, with some JNI if needed.

As sidenote, Kubernetes was started in Java and only switching to Go after some Go folks joined the team and advocated for the rewrite, see related FOSDEM talk.