The goal is to boostrap the compiler. So we need two things: the source code, and the compiler which understands it. If the compiler which understands it is i

The goal is to boostrap the compiler. So we need two things: the source code, and the compiler which understands it. If the compiler which understands it is in some widely used language, things are easier because we likely already have it. If we don't have it, it's likely nicely packaged. We also likely have it on a platform where that language we are trying to build has not been ported. That gives us a big head start in porting.