The defeat of the Marathas by the British can be attributed to several key factors.

1. Lack of Unity: The Maratha Empire was a confederacy of various regional powers, each with their own ambitions and interests. This lack of unity and coordination made it difficult for them to effectively counter the British.

2. Superior British Military Tactics: The British had a well-organized and disciplined army, which employed advanced military tactics and strategies. They also had superior firepower, including modern artillery and muskets, giving them an edge over the Marathas.

3. Economic Exhaustion: The Marathas had been engaged in continuous warfare for several decades, which had severely depleted their resources and exhausted their economy. In contrast, the British had a strong and thriving economy that enabled them to sustain their military campaigns.

4. British Diplomacy and Alliances: The British were adept at exploiting internal divisions within the Maratha Empire and forging alliances with rival factions. They successfully played off one faction against another, weakening the Marathas from within.

5. Lack of Naval Power: The Marathas did not possess a strong navy, which limited their ability to challenge the British dominance at sea. This allowed the British to easily transport troops and supplies, further strengthening their military position.

6. Leadership and Political Instability: The Maratha Empire witnessed leadership struggles and political instability during the late 18th and early 19th centuries. This weakened their central authority and hindered their ability to effectively resist the British.

Overall, the combination of superior military tactics, economic exhaustion, internal divisions, and diplomatic maneuvering by the British contributed to the defeat of the Marathas.