Why is Machiavelli considered the first political realist?

What will be an ideal response?

The emphasis on virtù extended to Renaissance rulers and society's leaders. As corruption and greed manifested in all positions of power, the Florentine diplomat and statesman Niccolò Machiavelli criticized those responsible for such failings. In his treatise, The Prince, Machiavelli argued that the need for a strong state justified strong rule. He pictured the secular prince as one who was schooled in war and in the lessons of history. The ruler must trust no one, least of all mercenary soldiers. He must imitate the lion in his fierceness, but he must also act like a fox to outsmart his enemies. Finally, in the interest of the state, he must be ruthless, and, if necessary, he must sacrifice moral virtue. In the final analysis, the end—that is, the preservation of a strong state—will justify the means of maintaining power, however cunning or violent.
The rules of power advertised in The Prince appeared to Renaissance thinkers not as idealized notions, but, rather, as expedient solutions based on a realistic analysis of contemporary political conditions. Indeed, Machiavelli's political theories rested on an analysis of human nature not as it should be, but as it was. His profound grasp of past and present history, made him both a critic of human behavior and modern Europe's first political scientist, one that based his cynical observations firmly in reality.