relationship between E.I.C. and the Indian states between 1756 to 1857

Here is the solution regarding your doubt- after military victories at the battles of Plassey (1757) and Buxar (1764), the EIC was granted the diwani of Bengal – control over the administration of the region and the right to collect tax revenue.

Additionally, The influence of the EIC in India started to grow as they got powerful in trade. The decline of the Moghul Empire was a significant factor that paved the way for the influence of the EIC in politics. They had a huge army that helped them engage in battles against other countries and side with certain rules.

Hope you found it helpful.