Introduction:
The Revolt of 1857, also known as the Indian Rebellion of 1857 or the First War of Independence, was a significant uprising against British rule in India. It was a complex event with multiple factors contributing to its failure. However, among the given options, the factor that was not responsible for the failure of the revolt was the rebels having a strong leadership.

Factors responsible for the failure of the Revolt of 1857:

1. Indians lacked a developed political consciousness:
- The majority of the Indian population at that time did not have a unified political consciousness or a clear vision of an independent India.
- The rebellion lacked a well-defined political objective or a coordinated plan of action.
- The absence of a common goal and lack of coordination weakened the rebellion.

2. The educated middle classes did not support the rebels:
- The educated middle classes, who could have played a crucial role in mobilizing support for the revolt, did not actively participate.
- They were largely influenced by Western education and had benefitted from British administration, which made them cautious about joining the uprising.

3. Infighting in the ranks of the rebels:
- The rebels were not united and there were divisions based on caste, religion, and regional loyalties.
- This internal conflict weakened their collective strength and hindered effective coordination of their efforts against the British.

4. Lack of strong leadership:
- The rebels lacked a unified and charismatic leadership that could effectively guide and inspire them.
- Although there were prominent leaders such as Rani Lakshmibai of Jhansi, Tantia Tope, and Bahadur Shah II, they were unable to provide a cohesive command structure and strategic direction.

Why D is the correct answer:
Among the given options, the factor that was not responsible for the failure of the Revolt of 1857 was the rebels having a strong leadership (Option D). In fact, the lack of strong leadership was one of the key factors that contributed to the failure of the rebellion. The absence of a unified leadership led to a lack of coordination, strategic planning, and unity of purpose among the rebels. While there were notable leaders, their individual efforts were not enough to overcome the challenges posed by the well-organized and disciplined British forces.

Conclusion:
The failure of the Revolt of 1857 can be attributed to various factors such as the lack of a developed political consciousness among Indians, the lack of support from the educated middle class, infighting among the rebels, and the absence of a strong and unified leadership. It is important to understand these factors to analyze the complexities of the revolt and its ultimate outcome in shaping the future course of the Indian independence movement.

The answer cannot be 'D' , because it was the major factor responsible for the failure of 1857 revolt. Option 'C' will be the correct answer for this.