Question

What is the rule of law? How can it help prevent tyranny?

Answer 1

Rule of tyrant. Kings make laws and change them when they want, enforce them or not.
The rule of kings can be changed to a rule of a dictator, or small group of people or even a government pretending to be a democracy.

The rule of law. People decide on a law. Everybody is subject to that law. The law may have come from a king or some tradition.