Based on the reminiscence of the first Hokages to rule in Konoha, stories and stories have been passed generations after, many historians have wondered and concluded, books have been written, the Rokudaime being given the most researching time, most sheets of paper with dates and possibilities, most people to write them. And it had nothing to do with his long career.
The most curious thing about the Rokudaime - which drawn so much attention towards him, hundreds years after - was the fact that people found it needed for him to be paid so much attention to begin with. To have the previous statement explained better, the Rokudaime, on the whole, has been described as the simplest of persons, with the simplest of minds, actually, a mind under the average, even if only compared to the other Kages to rule before and after him. The Rokudaime has been described as a plain, kind man, an open book, the kind of person of whose decisions and orientations could be easily guessed and understood.
Even though the man, known under the name of Uzumaki Naruto, after the biggest and most discussed war ever known in history, has been praised as the person to end it and bring the world victory and safety, followed by movements towards world peace, and even achieving that to an extent, no writer ever tried to hide that Uzumaki Naruto was neither smart, nor especially gifted.
Right after his death, explanations and dates have started being looked for, but Uzumaki Naruto, as expected from an Uzumaki, outlived all of his comrades - those people who could have ever known the actual truth - and only poor speculations have been made and that was not considered satisfactory enough. On the Rokudaime's farthest past, the next generation had not much to say. Sure, they knew the historical events, but that was just the shell. Nor the children of the Hokage himself or the children of his friends knew the personal side of the war. "Otousan always said, 'The war we've been through has nothing to do with the fairytales before going to sleep, of neither you, nor my future grandchildren'," the Rokudaime's daughter, already old herself, commented on the matter.
Writers wanted to know who the Rokudaime was before receiving his robes, hoping to link that to what they had. Because what they had, dated on closer times, was rather confusing. And what these children and grandchildren of his or his friends would say, about family memories and the way they remembered him, seemed to miss a few things. Apparently, the Rokudaime could not be remembered as extraordinarily smart, with impressing IQ (even though the life lessons they learnt from him showed wide experience and wisdom), or possessing incredible powers (new generations, leaving mostly in peace, did not ever see the Rokudaime fighting seriously), or ever being especially serious, cold-blooded, but the events history attributed to his thinking and actions spoke differently.
What they needed to know was that Uzumaki Naruto was not especially smart, indeed. That he had not been, most of the time, especially powerful, indeed. But the special thing about the Rokudaime was that he still somehow found the witty ways to do what's good, better and best for the ones he loved. The tricky part here was that Naruto loved his family, his friends, his enemies, his village and his world.