Why did they preserve the statue of Marcus aurelius?

Answer 1

Statues of emperors have not survived because they were melted to reuse the bronze in the Late Empire or were destroyed by medieval Christians because they felt that they were pagan icons. The statue of Marcus Aurelius survived because in the Middle Ages it was thought that it was the statue of Constantine I, who was thought to have been the first Christian emperor. In the 8th century it was kept in the Lateran palace, which back then was the residence of the popes. It was moved to its current location of the Piazza del Campidoglio on the Capitoline Hill in 1538 when Michelangelo redesigned this hill. The statue you see now in that square is a replica. The original one is kept in a museum, the Musei Capitolini to protect it from pollution.