What could be the reasons for the confidence of the British rulers about their position in India before May 1857?

In the Mid-18^th century, the power of Rajas and Nawabs were declined. Many kingdoms were forced to enter into a subsidiary alliance with the British.

Later with the policies of the doctrine of lapse and subsidiary alliance, the East India Company slowly took control over the kingdoms one by one. From 1757 to 1857, the company successfully annexed various Indian states without using military power. They got the Diwani rights of Bengal also.

The decline of the Mughal dynasty was another reason for the confidence. They also decided that Bahadur Shah Zafar would be the last Mughal emperor and his descendants were known as later Mughals.

Another reason was that except British company there was no other dominant authority in India.