i giggled when i found out Prevost had chosen the name Leo XIV. here’s a TL;DR on Leo XIII:
❝ Commonly known by the title “On the Condition of the Working Classes,” the lengthy “Rerum Novarum” sets out a body of papal teaching in response to the state of industrial society in the late 19th century. In doing so, says Catholic writer Robert Royal, Pope Leo’s 1891 encyclical “has shaped Catholic social teaching ever since.”
https://catholicreview.org/who-was-pope-leo-xiii-the-father-of-social-doctrine/