I heard that Rust was meant to capture the spirit of the language. It was meant not to have a lot of knew ideas (although, as it turns out, language design always leads to new ideas). We have a sort of informal rule to not include research that's less than 10 years old, so we can build off of ideas that have had a chance to prove themselves. We're bending that rule a bit now, of course. The idea was that Rust would codify and provide language support for patterns that have worked well in making large software like Firefox fast and safe.