India has long been one of the two biggest customers for Russian weapons. Since China was cut off (for stealing Russian tech) over the last decade India has become the major customer (accounting for 25 percent of Russian arms exports). But now Russia is rapidly losing the Indian market, which it has dominated for decades.
Russia became the main supplier of weapons, not because their stuff was better (it wasn’t) or cheaper (if often was) but because throughout the Cold War India positioned itself as the leader of the unaligned nations. In practice, India leaned to the left and obtained most of its imported weapons from the ideologically similar Soviet Union. India wanted Western arms but was unable to get the technology transfers it demanded (in large part because the Indians were not trusted and it was feared the tech would end up in Russia).
So, in the early 1960s, modernization of the Indian armed forces took place with Russian assistance. By the end of the Cold War in 1991, seventy percent of Indian Army tanks and artillery, eighty percent of warplanes, and eighty-five percent of warships were Russian. That has since declined by over twenty percent as India chooses more expensive but more effective and reliable Western gear.
India is very unhappy with Russian sloppiness in handling large projects, like refurbishing a decommissioned Cold War era carrier for them. This project has been a financial disaster for India. Worse yet, as India has bought more Western (Israeli, European, and American) weapons they have noted the differences in performance and service. Even Russia has had a hard time absorbing Western tech and continues to lag behind the West in military equipment effectiveness and reliability. India has found that Western tech is not only superior but transfers more readily than the Russian stuff and is more of a benefit to the overall Indian economy. The Israelis in particular have been good at doing joint development projects with India and transferring technology and manufacturing capability. Russia has not been able to change a lot of old habits quickly and completely and their flourishing arms export business with India is disappearing.