If the goal is to break the dependency cycle, a higher level language like Python would make development much easier. C++ is powerful, but not as rapid to develop in.
It's clearly easier to make a compiler in a higher level language (Python is just an example, but Lisps are suited to this kind of thing). For example, text parsing is easier in Perl/Ruby/Python/Swift/etc. As someone who knows C++, more thought is required to do the same thing as in a higher level language, although it runs much faster. If you just wanted to bootstrap the compiler, then you'd choose the easiest route to that. It could also be easier to read and understand than a C++ compiler.
It's clearly easier to make a compiler in a higher level language (Python is just an example, but Lisps are suited to this kind of thing). For example, text parsing is easier in Perl/Ruby/Python/Swift/etc. As someone who knows C++, more thought is required to do the same thing as in a higher level language, although it runs much faster. If you just wanted to bootstrap the compiler, then you'd choose the easiest route to that. It could also be easier to read and understand than a C++ compiler.