Final answer:
The main factor in Orwell's decision was the societal pressure to assert his authority in a colonial context.
Step-by-step explanation:
The main factor in Orwell's decision to shoot the elephant, as depicted in his essay 'Shooting an Elephant,' was the pressure he felt from the Burmese people to assert his authority as a colonial police officer. The immense influence of the crowd's expectation and his own internal struggle with the imperialistic role he played in their society forced his hand. Despite his personal feelings and the elephant's calm behavior after its rampage, Orwell felt compelled to act in accordance with the expectations of the locals and his position, illustrating a profound criticism of colonialism and the devastating impact of societal pressure.