Answer:
Due to alliance with the British and well trained army.
Step-by-step explanation:
Haider Ali and Tipu Sultan were skilled in warfare but still were unable to defeat the British because British has well trained army and alliance with Marathas and Nizam who has the strong armies. The presence of traitors in the army and government also contributes in the failure to defeat the British. If there were no alliance with the British, faithful army and ministers with Haider Ali and Tipu Sultan then Haider Ali and Tipu Sultan were able to defeat the British.