When we talk about the people living in Satyug what comes in your mind ? In terms of morality , it was the era of truth , justice and humanity. Everyone considered each other as their family. People took care of the nature. God Vishnu's first avatar came on the Earth - The Matsya Avatar , after that Hayagriv , kurm and so on.
In Tretayug , morality still stood on its three legs. It was the era of mankind. But some evils were born on Earth. To end them , Lord Rama came as an incarnation of Lord Vishnu. Some people even link Tretayug with Ramayana.
Then came the Dvapara Yuga, with Lord Krishna's Leela and Mahabharat. Wrong doings increased faster. Sadyantra and Maya was embraced in people moreover. Clues of Kalyug were mostly derived from this Yuga , how should we behave with people , our duties,etc. in the form of our most beloved - Shreemad Bhagvad Geeta.
Kalyug the present era. People forget their duties , responsibilities and Respect. No one cares about others , Everyone is egocentric. Very few real Mahatma and saints are left. Now , is god about to come here ???...