The R packages plyr/reshape2 and subsequently dplyr/tidyr. Data manipulation in base R can be pretty painful (awk arguably even more so, and Pandas didn't exist

The R packages plyr/reshape2 and subsequently dplyr/tidyr. Data manipulation in base R can be pretty painful (awk arguably even more so, and Pandas didn't exist yet), and going from that to an environment that's syntactically the nicest option available today for complicated manipulations of tabular data was a game changer. I know it's become fashionable to hate on the Tidyverse lately, but IMO it's the single biggest reason (though there's also a very long list of smaller reasons) that R is still relevant in industry.