The phrase, “Je pense, donc je suis” was written by René Descartes in 1637. Descartes asserted that « the very act of doubting one’s own existence served—at minimum—as proof of the reality of one’s own mind; there must be a thinking entity—in this case the self—for there to be a thought. »
The French, according to Cultural Insights https://www.iorworld.com/resources/france/ , have an individual orientation. Individual success leads to well-being of the group. Teamwork and group identity are important, but each individual is responsible for his/her own decisions and productivity. So ‘I think, therefore I am’ contributes to the well-being of the community.