It is my impression (as an outsider watching CF) that they have a bit of a not-invented-here problem. So if CF already has a culture of rewriting things, then rewriting it in Rust is not such a bad idea.

The problem is more that rewriting code that has a long history and is in wide-spread use tends to lose that history and any real world experience embedded in the code.

But if otherwise they would have written something in C++ then that point is moot.