Basis for the Colonial Monopoly

Robert Clive, 1st Baron Clive, became the first British Governor of Bengal.
Basis for the Monopoly:
The Seven Years' War ( 1756-1763) resulted in the defeat of the French forces, limited French Imperial ambitions , and stunting the influence of the Industrial Revolution in French territories. Robert Clive, the Governor General, led the Company to a victory against Joseph francois Dupleix, the commander of the French forces in India , and recaptured Fort St George from the French. The company took this respite to seize Manila in 1762. By the Treaty of Paris (1763), the French were allowed to maintain their trade posts only in small enclaves in Pondichery, Mahe, Karikal, Yanam, and Chandernagar  without any military presence.
Although these small outposts remained French possessions for the next two hundred years.
French ambitions on Indian territories were effectively laid to rest, thus eliminating a major source of economic competition. In contrast the company, fresh from colossal victory , and with the backing of a disciplined and experienced army, was able to assert  its interests in the Carnatic region from its base at Madras and in Bengal from Calcutta, without facing any further obstacles from other colonial powers.
Military expansion :

The Company experienced resistance from the the local rulers during its expansion. Robert Clive led company forces against Siraj Ud Daulah, the last independent Nawab of Bengal, Bihar, and Midnapore district in Orissa to victory at the Battle of Plassey, since Siraj Ud Daulah was a Mughal feudatory ally. But the Mughal empire was already on the wane after the demise of Aurangazeb, and was breaking up into pieces and enclaves.After the Battle of Bauxer, Shah Alam II, the ruling emperor, gave up the administrative rights over Bengal, Bihar, and Midnapore District. Clive became the first Governor of Bengal.