The country that provided aid and technical assistance for steel plants in India is the USSR (Union of Soviet Socialist Republics).

Reasons for USSR's aid and technical assistance to India's steel industry:

1. Historical Friendship: India and Soviet Union shared a long-standing friendship, which was based on mutual trust, respect, and cooperation. The USSR was one of the first countries to recognize India's independence, and since then, they have had close diplomatic and economic relations.

2. Cold War Politics: During the Cold War era, India was a non-aligned country, which meant that it did not align itself with either the US-led Western bloc or the Soviet-led Eastern bloc. However, India leaned towards the Soviet Union as it provided aid and technical assistance to India's development projects, including the steel industry.

3. Industrialization: India's steel industry was in its nascent stage after the country's independence in 1947. The government of India realized the importance of developing the steel industry as a key sector for the country's industrialization. However, India lacked the technical know-how and capital for developing the industry. The USSR provided aid and technical assistance to India's steel plants, which helped in the development of the steel industry.

4. Economic Assistance: The USSR provided economic assistance to India in various forms, including grants, loans, and technical assistance. The economic assistance from the USSR helped India in its economic development, and the aid and technical assistance for the steel industry played a crucial role in the country's industrialization.

Conclusion:

In conclusion, the USSR provided aid and technical assistance to India's steel industry, which played a crucial role in the country's industrialization. The historical friendship between the two countries, Cold War politics, industrialization, and economic assistance were some of the reasons for the USSR's aid and technical assistance to India's steel industry.