In 1564, the theologian Pierre Viret denounced that there existed in Italy a group of people who called themselves Deists:
“They call themselves Deists, a completely new word, which they want to contrast with Atheist. Because “atheist” means a person who is without God, while they want to make it clear that they are not without God at all, since they certainly believe that there is some kind of God, whom they even recognize as the Creator of heaven and earth.”
45 years earlier Leonardo Da Vinci died, whose thought can undoubtedly be placed within Deism. In fact, Leonardo was not an atheist, but he didn't even believe in the Church, indeed he despised it, even though he worked for it. When Leonardo speaks of God, his identity as a deist ante litteram appears evident.
There is no evidence to say so, but it makes us think that Leonardo Da Vinci, through his disciples (such as Andrea del Verrocchio, Giovanni Antonio Boltraffio, Giacomo Caprotti, known as Salaì, and Francesco Melzi) may have contributed to giving birth to the community of self-proclaimed "deists" that Viret speaks of.
For this reason, in Italy we like to think that Leonardo Da Vinci can be considered in all respects a progenitor of Deism. If anyone found some useful element to support this thesis, it would be of great interest.
From what you wrote I believe that you are correct that Da Vini may have been the one who is responsible for Deism in Italy. Deism in General is considered to have been founded in the 17th century in England which may explain why so many of our Founders in the United States were Diests.