I suspect that has as much to do with the maturation of the data science community as it does the language environment. There have been pockets of R users who put much effort into reproducibility before the era you cite, such as Bioconductor.

When I think back to the era you're describing what I recall was people winging around hacky scripts being the norm regardless of their environment. While still not something I'd think of as software engineering best practices, what I see now is less Wild West.