Hey there,
Bungie is investigating player reports that the Student of History Trophy/Achievement is not unlocking properly. Bungie recommends players to follow the troubleshooting steps listed within this Help Article: https://www.bungie.net/7_A-Trophy-or-an-Achievement-did-not-unlock-in-the-g/en/Help/Article/12242
If this does not resolve the issue, please post a report in this thread: https://www.bungie.net/en/Forums/Post/213318340