Prosperity resulting from trade and commerce are what frequently generate art. Florence must have been a rich flourishing city based on the incredibly high level and extraordinary quality of the art I saw.
The reason Old Friend Charlie located the beginning of modern commerce in Florence in the late 11th century is because that is where Fibonacci first published his book on multiplication. The book sold widely and was the core tool that permitted business people to calculate percentages and interest rates.
There is also evidence that double entry bookkeeping was in use in Florence at this time. One example was the Giovanino Farolfi Company whose books show evidence of credits and debits.
With business people able to do multiplication and double entry bookkeeping I am convinced that Florence is the location for the inception of modern commerce. The shipping port for Florence is Pisa.
I highly recommend the Florence exhibit at the Getty.