Eighteenth Century [India] was an age of political upheaval in India. Large scale political transformations were witnessed in this country in this century.
During the eighteenth Century due to the decline of Mughal Empire and emergence of new forces (politico-military) there was a COMPLEX power struggle going on. That is, there were multiple actors at different levels.
In the Mughal Court ‘Nobles’ were turning kingmakers. For eg, Sayyid brothers, Imad-ul-mulk. They wanted to establish their domination over the Mughal crown. In the regional kingdoms, for eg, in Bengal the ambitions of Nobility such as Mir Jafar and others was quite clearly visible.
The Central Authority [which was the Mughal Court] was challenged by Regional powers which led to emergence of succession states. Eg: Bengal in East India, Awadh in North India, Hyderabad in the Deccan.
The Great Indian Regional Powers were fighting against each other. This is termed as the INTERNECINE Struggle. Internecine struggle refers to struggle within a group (in this case the land of India) which is destructive to both sides at the end. To add to the woes, India was also challenged by foreign invaders around this time, namely, Nadir Shah, Ahmed Shah Abdali.
Given the defeat of Marathas at the third battle of Panipat a political vacuum was created. The Complex Power Struggle which was already happening along with a weakened Central Authority gave way to easy overtaking by any external power body. This new power was to be the East India Company.
The Company did not have to face much struggle. Ground was fertile to use Divide and Rule. First they used Mir Jafar against Siraj-ud-Daulah in the Battle of Plassey. Once the authority of Bengal was gone they played foul with Mir Jafar. Similarly, they conspired to play one regional power against another. They did not stop here. They later used this policy to play one community against another and then one religion against another. Through this, was eventually laid the foundation of British Empire in India.