Avatar comes in order to uphold Dharma

In Bhagavad-Gita, Lord Sri Krishna, the Avatar of the Dwapara Age, declares thus:
"Yada Yada Hi Dharmasya Glanirbhavathi Bharatha Abhyukthanam adharmasya Thadathmanam Srujamyaham.”“Parithranaya Sadhunam Vinashaya cha Dhushkrutham Dharma samsthapanarthaya Sambhavami Yuge Yuge"
Whenever there is a decline of Righteousness and rise of evil, the Lord incarnates from time to time to uphold Righteousness, to protect the Virtuous and to uproot the evil.
The Avatar appears whenever the world is passing through a spiritual and moral crisis. The Avatar comes in order to uphold Dharma (Righteousness) and raise the universal consciousness