Why should India join SCO and support China when China keeps on opposing India's NSG & UNSC memberships while adopting string of pearls strategy against India.
India & Russia do not have any direct conflict or overlapping interests but Russia by align with China meant that Russia is indirectly align against India.
Conspiracy Theory: In spite of the breakup of USSR, Russo-Indian relations continued to get strong. This gave way to the formation of G2. the objective was to break the Indo-Russian relations by pulling them in opposing directions.
China started pulling Russia towards itself while US has started pulling India towards itself.
Return of the G2: Can US and China run the world? - Telegraph