If I remember correctly, Nehru had several communist sympathies -- or at least, was very tied into and involved with the Soviet Union. Also the U.S. had, in the post-Nixon era, greater ties with China, and hence the Soviets were open to trade with India.
Of course, politically, India were quite foundational in the Non Aligned Movement, which spared it from much of the political angst of the West.
Noteworthy to this effect, is the brief (one of the shortest in history) Portuguese-India war (can't remember the exact name), over the colonial possession of Goa, a short while after independence. During the ensuing panic meeting in the UN over the invasion of Portuguese holdings, the primary defender of India in the UN Security Council was in fact the Soviet ambassador, who consistently used its veto power to protect India from UNSC action.
Adlai Stevenson, the American ambassador, on the other hand, adhering to the philosophy of postwar idealism in international diplomacy, condemned India's actions, asserting that they should have instead sought recourse through peaceful means.
It appears that from independence, the Soviets were eager to capitalize off of open markets in India, and consequently were inclined to make political friendships with Nehru (who was eager to reciprocate). The US and the West had less of an inclination to do so, seeking markets in other developing countries.
Perhaps the development of a consumer culture in the West helped encourage this inclination-- while American businesses and consumers enjoyed a prosperous ecosystem, the Soviet-style communist system operated differently, and perhaps there was a greater desire for foreign markets there than in America, where the domestic market was promising enough for many businesses.
Also, the Soviets had more to gain in spreading their ideology to India, which from its inception was a bastion of democracy. The US had less of a fight to preserve capitalism/democracy there. Had India gone communist, it would have been a big win for the USSR.
But the US was fairly confident in India's post-Independence culture and economy, so had less of an impetus to fight a war of economics there by actively encouraging trade abroad in that particular country. And, heck, it would seem the Soviets got somewhere, with the communist party in Bengal still being a political force to this day.