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.