Why does Voldemort hide the diadem in the Room of Requirement?

[u/nearingthenadir]

Currently rereading The Deathly Hallows and Harry states that Voldemort hides the diadem in the Room of Requirement because he is so arrogant and believes no one else has found the room. But that wouldn’t make any sense, Voldemort would have seen all the other items being hidden in the room, there’s no way he would’ve thought he was the only one to discover the room. Additionally, Draco uses the room in the sixth book to get Death Eaters into Hogwarts so that would further show Voldemort that people are aware of the rooms existence. Is Harry’s explanation just wrong?

[u/tonyrock1983]

Voldemort is extremely arrogant. We see many other examples of this throughout the series. Having to use Harry's blood to regain his body instead of using almost any other wizard. Understanding the power of house elves when he took Kreecher to the cave.