1. The Medici’s paid for it
Bartolomeo Cristofori who is credited with the initial invention worked for Ferdinando de’ Medici, Prince of Tuscany. Fernando was born in 1663 and so by then the Medici had already financed much of the Florentine led renaissance. Cristofori’s job title was keeper of the instruments and he used his understanding of the harpsichord keyboard to develop something new.
2. German technologists picked it up and ran with it
German instrument builders discovered an article written in Italian which explained the basics. They immediately grasped the possibilities and developed a key innovation, the sustain pedal. The pedal means one chord can be continuing while something different is being played, creating the unique capabilities pianos have.
3. The Industrial Revolution developed the technology for piano strings
The Industrial Revolution is responsible for huge advances in technologies which went on to be used elsewhere. One unforeseen consequence was developments in musical instruments.
Piano makers needed better techniques for creating tension and higher quality wire. Both were possible by using advancements which were made for other reasons. Essentially the same technology, but with some tweaks, is the expertise of modern piano repairman Birmingham.
4. Johann Sebastian Bach was a first critic
Initially JSB was not too impressed. He felt the upper notes were too soft and quiet. It was reasonable given that he was the most famous organ composer of his day. His harpsichord piece the Goldberg Variations is now one of the most famous for the piano.
5. American ingenuity added cast iron
As strings got better, the tension they created was problematic. Alpheus Babcock patented the single piece cast iron frame in 1825. Now the piano could support the tension modern strings need, which can be a massive 20 tons.