Why did the king of Macedonia manage to conquer Greece? Why did Alexander the Great conquer half the world?

The king of Macedonia managed to conquer Greece, since the Greek city-states were not united in the fight against his country. Alone, they could not normally resist the troops of Tsar Philip. Alexander the Great was able to conquer vast territories, thanks to the special structure of his army. It was called a phalanx and at that time was an irresistible force for most of the opponents of Macedonia. The Macedonian army was also well equipped, trained and able to quickly execute commands and obey the orders of the commander.