This trophy/achievement is not unlocking for a lot of people even after switching account, logging out or even fulfilling the requirements of such trophy/achievement once again.
Want more proof this trophy/achievement is not unlocking for a lot of people? Here's a list of such topic across Reddit, Bungie.net and even other forums.
https://www.bungie.net/en/Forums/Post/214612645
https://www.bungie.net/en/Forums/Post/214710441?showBanned=0&path=0
https://www.bungie.net/en/Forums/Post/214616623?sort=0&page=0
https://www.reddit.com/r/DestinyTheGame/comments/55ueoq/student_of_history_trophy_is_bugged/?ref=search_posts
https://www.reddit.com/r/DestinyTheGame/comments/55t00l/student_of_history_achievement_not_unlocking_xb1/
https://www.reddit.com/r/DestinyTheGame/comments/55wrcl/student_of_history_trophy/
http://www.xboxachievements.com/forum/showthread.php?p=6827111
https://www.reddit.com/r/DestinyTheGame/comments/55ta2l/student_of_history_achievement_not_unlocking_on/
http://psnprofiles.com/forums/topic/41709-student-of-history-bugged/
http://www.playstationtrophies.org/forum/destiny/296772-iron-lord-artifacts-glitched.html
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Hello, We are investigating player reports that the Trophy/Achievement “Student of History” is not unlocking when players collect and attune all Iron Lord Artifacts. If you are currently experiencing this issue, please follow the troubleshooting steps within this [url=https://www.bungie.net/7_A-Trophy-or-an-Achievement-did-not-unlock-in-the-g/en/Help/Article/12242]Help Article[/url]. This may resolve the issue for some players. If it does not, please report your issue to the [url=https://www.bungie.net/en/Forums/Post/213318340?sort=0&page=0]Destiny: Rise of Iron Known Issues[/url] thread. The pinned thread will be updated when additional information is available.