To explain why the Congress was defeated in the Lok Sabha elections of March 1977, we need to look at the political context of that time.

- **Internal Emergency (1975-1977)**

The main reason for the defeat of the Congress in the 1977 Lok Sabha elections was the imposition of the Internal Emergency by Prime Minister Indira Gandhi in June 1975. During this period, civil liberties were suspended, political opponents were arrested, and censorship was imposed on the media. This move was widely criticized and led to a backlash against the Congress party.

- **Opposition Unity**

Another significant factor that contributed to the defeat of the Congress in the 1977 elections was the unity among opposition parties. Various opposition parties came together to form the Janata Party, which provided a strong alternative to the Congress. This unity helped in consolidating anti-Congress votes and led to the defeat of the Congress in the elections.

- **Anti-Incumbency Sentiment**

The imposition of the Emergency and the authoritarian rule of the Congress government under Indira Gandhi had created a strong anti-incumbency sentiment among the voters. The public was disillusioned with the Congress party and its leadership, which reflected in the election results.

- **Economic Issues**

Apart from political factors, there were also economic issues that played a role in the defeat of the Congress. The country was facing economic challenges during that period, including inflation and unemployment, which further fueled the discontent against the ruling party.

In conclusion, the defeat of the Congress in the Lok Sabha elections of March 1977 can be attributed to a combination of factors, including the imposition of the Internal Emergency, opposition unity, anti-incumbency sentiment, and economic issues. These factors collectively contributed to the downfall of the Congress party in that election.