Buddha's night before enlightenment According to the historical story before the day of enlightenment, Mara apparently lured the Buddha with various worldy pleasures. Now, I am not arguing whether Mara really existed or is just Buddha's mind (which would be rather my interpretation). But The Buddha should at that time be a non-returner and he must have abandoned the fetter of sensuous desires. He should've chilled in the 4th Jhana not giving a damn!

So my question is: Why was it a struggle for the Buddha if the conditioned fetter of sensuous desire was already uprooted as an anagami?
In my understanding, Buddha did not progress through the four stages of enlightenment he later prescribed for his students.

This is because, for Buddha students - you start with theoretical understanding (stream entry), and then you practice according to instructions until you achieve it (arahant-hood).

In Buddha's case, because he is Self-Awakened, he starts with intuitive practice and then achieves understanding (Bodhi). 

So in Buddha's case he does not proceed gradually, phase by phase, like assembling the puzzle by looking at the complete picture. Instead, it's like solving a puzzle randomly - by the time he sat under the Bodhi Tree, he had assembled most of the pieces but still did not know what was shown on the picture.

This is why in Buddha's case he left all interpretative possibilities open until the last moment, which means he still had doubts until the very last moment. Those doubts are represented in the anthropomorphic personification known as "the Mara".

In case of Buddha's students, the interpretative framework is locked in place from the time of stream-entry, so doubts are eliminated at that phase.