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human
[Lord of the Rings] How have none of the fellowship heard about the sacking of Moria and the death of Balin?

Judging from the skeletons and state of Moria, it's safe to assume it happened a while back - is the Dwarven loss of Moria not big enough to be news across Middle Earth - or at the very least news for Gimli, Legolas and Aragorn? Also Gandalf knows about the Balrog, why does nobody else?

Edit: some great answers, thankyou. Seems I completely forgot the dwarves lost Moria long ago, as mentioned in the hobbit. Balins expedition was to reclaim the mines!
gpt
So, it's important to note that in the book it's assumed that the expedition has failed. Gimli isn't hyping a royal welcome, he wants to find out why they haven't heard from the expedition in years.

You're also assuming communication is widespread but that is not the case. Events like the Council of Elrond are very rare and races rarely ever communicate. The path through the Misty Mountains that would take you near Moria is rarely used due to the existing danger of orcs.

So it's just that nobody knew what happened and nobody investigated until the Fellowship was forced there. Because why risk the soldiers, you have other problems to worry about.

Gandalf also didn't know exactly what was down there, he just suspected that Durin's Bane was a balrog. As soon as they see it in the book, Legolas identifies it as a balrog. This makes sense because balrogs date back to the earliest wars between elves and Morgoth so Legolas would have heard descriptions of balrogs growing up and this is why in the movie as soon as it's revealed the camera zooms on Legolas.

As for why Gandalf is the only other person in the Fellowship who can identify it, he's even older than Arda (Earth) itself and was one of the Ainur who helped sing the universe into existence. He has ancient knowledge and is imbued with more powerful magic than elves or men.