Final answer:
The question seems to blend fictional content with historical context. There is no historical record of a flag of L'Manburg or a figure named Niki related to the provided historical events, suggesting the question may pertain to fictional or entertainment content rather than a factual historical event.
Step-by-step explanation:
The question 'Who burned down Niki's flag of L'Manburg?' is unrelated to the historical content provided, indicating possible confusion between a historical event and fictional or entertainment content. The information provided about Jacob Leisler's revolt and subsequent events in New York's history or the provided literary descriptions of fires and destruction do not pertain to a figure named Niki nor to a known historical place called L'Manburg. It appears to be a case of mistaken context or a blending of fictional narrative with historical elements.
For accurate historical insight, it is important to reference actual events and figures from history. If the query is related to fictional content or events from a game, film, or book, it would be best to seek sources directly related to that medium for a precise answer.