None of those dictators needed Machiavelli for them to know how to act. Ruthless dictators and tyrants existed well before Machiavelli, and will exist regardless if they have access to his writing.
The answer is, as Duggeh said, the invention of the printing press. Even as important as the Agricultural Revolution was in 10,000 BC or so, it was the ability to easily transmit massive amounts of information that most shaped how the word is today. Without knowledge, we are nothing. You could even make an argument for the invention of the internet, but that would still be more of an extension of the printing press than anything.
Even the number 2 most important event, the Enlightment, was simply an outgrowth of the access to knowledge that the printing press allowed.
The answer is, as Duggeh said, the invention of the printing press. Even as important as the Agricultural Revolution was in 10,000 BC or so, it was the ability to easily transmit massive amounts of information that most shaped how the word is today. Without knowledge, we are nothing. You could even make an argument for the invention of the internet, but that would still be more of an extension of the printing press than anything.
Even the number 2 most important event, the Enlightment, was simply an outgrowth of the access to knowledge that the printing press allowed.





















