Board Thread:Naruto Discussions/@comment-26708623-20161103030058/@comment-734582-20161103082418

Because the manga would be 1200000 pages long if he explained everything about everyone. We'd still be in Part 1's chunin exams if he went that way.

Considering there's no man famous for striking down Hashirama it's possible he either died through other causes or was unceremoniously assassinated through, say, poison.

Kinkaku and Ginkaku's deaths aren't clear either. They were famous enough to go into the history books as heroes and only later were seen as villains, so it's probable that they died a heroic/villainous death. if memory serves, they were dead in Hashirama's era so it's very probable their killer was lost to history.