Why ask why?
Why did the US invade Iraq?
Why did N Korea invade S Korea?
Why did did Japan invade Manchuria?
Why did the Soviet Union invade Finland?
Why did Germany invade Belgium?
Why did France invade Spain?
Why did England invade France?
Why did the Turks invade Europe?
Why did the Moors invade Spain?
Why did Spain invade the Incas?
Why did Macedonia invade Greece?
Are you insinuating that none of those countries had reasons to go to war on any of those occasions? Are you conflating Germany invading Belgium to China invading a country 300 times the size of Belgium and twice China's GDP? Are you conflating pre modern warfare to modern warfare, where Afghanistan or Iraq can financially cripple super powers in less than a decade?