Florence was very important during the Renaissance because it was a major center of Renaissance culture. For example, the three men who some say were the greatest writers of the era were from Florence. These were Dante, Petrarch, and Boccaccio. There were many churches with Renaissance religious art as well.
All of this was possible because of Florence's dominance of the wool trade. Wool from the area around Florence was sold all over Europe and even over to the Middle East. This brought a lot of money to Florence, which allowed rich people to support artists who made Florence important.
Florence was an important city during the Renaissance. The Renaissance first began there and was very strong in Florence. As the Renaissance spread throughout Europe, Florence became a model for other places to copy.
Florence was very prosperous during the Renaissance. There were many guilds that were very successful in Florence. The textile guild was very powerful. Florence became a very wealthy city because of the trade of textiles, especially the trade of wool. The workers took untreated and unfinished wool from other places and worked it into high quality wool that was sold in many places.
Florence was also an important banking center. Florence wasn’t a port city, so banking became an important industry. Florence’s bankers had influence throughout Europe.
Culture also flourished during this time in Florence. Its artists and writers became very well known.
As a result of these factors, Florence was an important city during the Renaissance.
The city of Florence during the Renaissance was under the control of the very enlighted and rich family of Medici, who together with other high middle class families (among others Pitti, Strozzi and Ruccellai) promoted a renewal of the city in particular promting art and culture. In particular figurative arts flourished both for the presence of patronage and great artists (such as Brunelleschi, Masaccio, Donatello at the beginning of Reinassance and Leonardo da Vinci, Michelngelo later).
Italian Merchants did so much money first of all because Itay had a very strategic geographical position in Europe, then the "Repubbliche Marinare" (sort of republican city-state based on sea trade) were an old institution that estabilished a lot of connection among Italians and merchants from all over the world.
(sorry for my English, but I'm not an anglophone speaker)