A relatively new explanation for much of the seeming "advances" of the Renaissance is that when the Ottoman's overan the Byzantine Empire in 1453 many merchants and craftsman fled to Venice, and thence to other parts of Italy. Venice was a center of commerce that their were already trade routes with.
The Renaisance then was, in some measure, a homecoming of the knowledge of the ancient Italians (the Romans) that had been transferred East by Constantine the Great, only to return over 1,000 years later. Famously the first dome built in Europe since antiquity was built in Florence in 1436. So the timing was good, Europe was back in the monumental construction business.
Thank-you: You short, but informative reply to my post makes me pine for our beloved Italia. I was planning our fourth and longest trip to Italy this fall when the Chinese Wuhan Flu broke out. My wife’s grandparents are from Campania, and her mother was born in the USA a few weeks after her grandparents immigrated here — legally — in 1935. When my wife recently received the results of her DNA test, she was perplexed to learn that her “Italian side” is mostly Greek, Turkish, Spanish, French, and Maltese. This came as no surprise to me given the historical fact that Italy — particularly southern Italy — has been an occupied territory for thousands of years.