I travelled to Florence a couple of years ago and bought a copy of Christopher Hibbert's, The House of Medici, it's rise and fall. A fantastic read.

There were a few things that contributed to the rise of the Medicis - Florence was a Republic, so they could build a power base there without having to crack through an entrenched aristocratic class. They did this in a fairly bloody manner, and the family was very nearly wiped out in this time by assassins.

Also, the Italian Peninsula itself was a collection of city states at the time, so there were many opportunities for advancement, trade and business. Some of these city states, especially Venice, were extremely wealthy through international trade.

Third, the Medicis were canny political power brokers and underwrote the careers of several Cardinals who became Popes. Sometimes this ended spectacularly badly, and they lost a lot of money through these loans which were never recovered.

Finally, they achieved a semblance of political establishment when they married into a Royal Family (The French) and became Dukes. But once they became aristocrats themselves, the family appears to have become quite conservative and their wealth ossified.

Very simplified analysis of this, so I really recommend you buy the book; it's a fantastic history.

Did a lot of the Medici family records survive compared to other families?

The systematic marriages and methods of holding initial investments over successful businessmen helped catapult them forward in the business world. Not every kid you finance is going to be a DaVinci or a Michelangelo...unless you make sure that they are...and that's what they did. They invested long term and forced their investments to become **the best. **