Why is the Acropolis crumbling ?
Actually, the Acropolis suffered from an attack by Russian warships when Peter the Great attempted to take the port city of Azov on the Black Sea. Peter was determined to create a "window on the west" for Russia, which at that time was landlocked except for the warm weather ports on the Arctic Ocean. His first attempt to do so was a war against the Ottoman Empire; by taking Azov, he would have access to the Black Sea, and by way of the Black Sea to the Mediterranean. In attempting to dislodge Turkish forces near the Acropolis, his warships opened fire on that structure, and demolished much of it. A view of the ruins makes it obvious that the destruction was not caused by erosion and the passage of time; such damage does not cause structures to break apart in large pieces as is the case with the Acropolis. Thus the cause of its destruction was rather the devastation of war rather than the lapse of time.
An excellent resource you might consider is Robert K. Massie's biography, Peter the Great.
There are many reasons that the buildings on the Athenian Acropolis, including the Parthenon, are crumbling. One reason is simply age; they have been there for over two thousand years. The original paint has faded due to ultraviolet radiation from the sun. The Parthenon was damaged when it was transformed into a church in the sixth century. Many buildings were damaged during the Turkish conquest of Greece and the subsequent Greek war of independence. The next problem is air pollution, which causes acid rain. Acid rain harms marble. Next, the vibrations from the heavy traffic near the Acropolis contributes to the damage. Finally, it is a popular tourist area, and the constant influx of people causes many forms of damage from deliberate vandalism to issues like the oil transferred from people's skin as they touch columns weakening the marble.
You are several hundred miles off geographically on this. The question refers to the Athenian Acropolis, not the city of Azov. Note that the Athenian Acropolis is a few miles inland from the port of Piraeus and could not have been fired upon by warships with 18th century technology.
Your argument is with Robert Massie, not with me, but thanks for the Geography lesson.