Both of these updates took advantage of major new innovations in the R ecosystem, including updates in rlang, vctrs and glue among others.
pivot_longer() and pivot_wider() to better manage and control transformations of dataframes from wide to long form - one of the most common data-wrangling tasks. Replacing gather() and spread(), these new functions introduced more capability to manage the specifics of the transformation, cutting time for users in terms of how they tailor their outputs.
introduction of across() and c_across() as adverbs to be used with summarise() and mutate() simplified the number of scoped variants that users needed to work with and, like the tidyr changes, allowed greater control of what the output looked like.