Why did Benjamin Franklin fly a kite during a thunderstorm?

In 1752, Franklin proposed an experiment with conductive rods to attract lightning to a Leyden jar, an early form of capacitor.

On June 10, 1752, Benjamin Franklin flies a kite during a thunderstorm and collects ambient electrical charge in a Leyden jar, enabling him to demonstrate the connection between lightning and electricity. Franklin became interested in electricity in the mid-1740s, a time when much was still unknown on the topic, and spent almost a decade conducting electrical experiments. He coined a number of terms used today, including battery, conductor and electrician. He also invented the lightning rod, used to protect buildings and ships.