Russian supporting India.

Historical
Before India's independence, there was literally no contact between the two nations what so ever. Central Asia, in present day Kazakh region was known due to trade routes but no major relations existed.

Independence Struggle of India
During the colonization period, a lot of efforts were made by Indians to educate. The heroes of this struggle were highly educated and well read. Bhagat Singh, who was only 23 at death, quoted Lenin & Marx several times. The hardships of capitalism and inequalities of Indian society attracted a lot of these educated freedom fighters to Socialism. The leadership of Pakistan back then was divided on what kind of a nation they will be. The freedom fighters who eventually became the leaders of free Pakistan had Socialist tendencies. But Soviet Union had basic problem with the religious line on which Pakistan was to be made as communists advocated atheism. Several calls for help from Soviets was denied during the independence struggle and struggle for a separate nation.

Indian Partition
The partition of India led to formation of Pakistan and India as two countries. The religious lines of division left a bitter relation between two nations, like all separations. After Partition, the Pakistan as a new Nation, saw a lot of Soviet influence in its neighborhood.  1950 Pakistan PM of time visited USA for the first time.

Cold War
Enter 1950s, post World War 2. Europe is destroyed. Japan & China are devastated. US & Soviet Union are the only powerful nations. Enter Cold War. Interesting to note here that US & Soviet Union both had started engaging diplomatically with both India & Pakistan.

After 1950 visit, USA realized importance of Pakistan's location to be right under the belly of Soviet Union & also China. Next 3 years saw a lot of visits of leaders between two Nations. This concerned India, who had already fought 2 wars with Pakistan by this time and lost a lot of territory in Kashmir to Pakistan. Militarily speaking, both nations had same stuff inherited from British era. The evolution of weapons started with US treaty of 1954 which was followed by large scale training of Pakistan armed forces by US. US saw a professional 4 million strong volunteer army to fight Soviet Union.

What was India doing? India started the Non-Alignment Movement. Amid the concerns of world war 3 starting in Korea, India came out with a policy to shun the big powers. However, India saw US arming of Pakistan as threatening and began to look for counter strategy. The only logical option available was Soviet Union. The Indian PM of time went to Soviet Union in 1955. Large scale military engagements did not start till 1960s where India suffered a humiliating invasion from China. To make matters complex, China and Russia had very close relations as Communist countries. Russia denied Mig-21 tech to China in 1962 but agreed to transfer tech to mass produce it in India. This soured China-Russia relations and India still feels indebted to Russia for it. Russia also supported India in 1965 & 1971 wars with Pakistan.

The ordinary Indian sees Russia as a friend who supported them through all their wars and a balancing act against US supply of arms in an aggressive & unstable Pakistan.
In the aftermath of 1971 war, Indian leadership realized the importance of an international outreach. Most of western nations followed what the US did and condemned India as the aggressor. They started engaging with more countries, specifically the powerful and developed western nations. Import of Jaguar aircraft & Mirage 2000 was seen as a big move away from Russian dependence. Things in recent years have shown a significant military imports from USA, Israel & France other than Russian hardware. But this recent developments have not shaken the base of Indo-Russian relations in the minds of average Indians.

Edit 1: In fact in the 19th century, the Tsars of Russia and the French thought of India as the reason for Britain's power and wanted to cut it off. Hence both the imperialistic powers attempted to occupy Persia and Afghanistan to invade India for its riches. Unfortunately, even today those two regions pay the price for ambitions of some nations.