That’s not really an “odd” situation, though. That’s kind of just how it goes. The culturally important texts like the Bible get copied and spread, but who cares about the government’s documentation? Literally no one, unfortunately. Preservation within the historical record is in large part a mix of media used and popularity; a popular text can afford to be written on less durable materials, but using those less durable materials for unpopular documents? And they’ll be lost over time.

It is odd here because the surviving records are so much better when you go even a little bit further in the past. Compare Sennacherib's siege of Jerusalem under King Hezekiah a century or so earlier. We have Judah's side of things recorded in Isaiah, II Kings, and Chronicles. We have Sennacherib's side of things recorded in his royal annals. When Nebuchadnezzar II actually succeeded in conquering Jerusalem a century later, we just have the Bible.