With printing press’s invention by Johannes Gutenberg allowed for far reach access to important secular books and literature and most importantly Bible. It became normal for common people to read and think in their own language. This meant vernacular-meaning their mother tongue- literature aided with the spread of humanistic ideas beyond intellectuals of the time. Writers like Petrarch and Dante wrote in Italian and believed everyone should be able to read in their languages.
Scientists also began to value observation over religious teachings and viewed everything with skepticism. They examined their theories by evidence. Even sometimes some scientists like Galileo Galilei gathered enough courage to speak out against the Church. But Renaissance didn’t exclusively meant separation from religion all together, rather abandoning old Middle Age values and bringing new insights to the human perception of life, art and everything.
Rhetoric was born as a consequence of this.