Ozymandias was a cruel and arrogant king who got his statue erected so that people would remember him even after his death. But with the passage of time, the condition of the statute became piteous, it was completely shattered. There were only the trunkless legs which remained in the wildness and nothing else was there which could show the greatness of Ozymandias, 'the king of kings'. It is ironical that a person who was so powerful and who looked down upon others, was reduced to a trunkless statue.
The poem leaves a message that wealth, power and position do not last forever. So, they should be used for the welfare of mankind and should not be misused. Time is the ultimate lever. One must realize that respect is never demanded. Real power is in winning hearts and not in ruling the weak and the needy. Time conquers all, so winning the hearts of people is the real victory.