Why did the huge Persian power collapse the clan by the onslaught of the Macedonian conqueror?

Why did the huge Persian power collapse the clan by the onslaught of the Macedonian conqueror? What was the strength of the Macedonians?

At that time, the Macedonian army was very strong and disciplined, hardened in many battles, it was a formidable force. For her invincibility, she needed only one thing – an outstanding military leader, who became Alexander the Great. Thanks to his talent as a commander and the ability to inspire his troops, he managed to defeat the most powerful Persian army in the world and reach India. True, the rule of the Macedonians did not last long; after the death of Alexander, the empire drowned in internecine wars.