Prior to this all of the tombs that had been discovered had already had significant robbing, likely centuries prior. While there was evidence that someone had been in KV62 post-closing of the tomb, very little was affected. Not only did this mean a treasure trove of artifacts that were buried to go with the King in his afterlife, but the body and sarcophagus were completely in tack as well, pretty much the holy grail.
The tomb itself was unusual as Tutankhamen died unexpectedly young and his burial place had not yet finished construction. It's believed that this was actually the tomb intended for his Grand Vazier, Ay. It was such a rushed job of burial that the items were in great disarray, a chariot cut apart to fit inside even. Prior to the discovery of the site in 1922, the location of his burial was under great debate. It was believed to have been found at KV54 where some artifacts dating to his time were found. It wasn't until Carter decided in a last effort to dig in an area covered with huts used by builders from a later kings burial that the real tomb was found.
It gained notoriety due to not only the contents of the tomb, but popular stories that there was a curse upon it, slowly killing off all that had disturbed it. Lord Carnarvon, Carters benefactor, died shortly after the room with the sarcophagus was opened and every subsequent death in the team (for various reasons) was considered to support this theory.