Virtue signaling, probably. Reuse of royal robes and regalia is common in English coronations. Usually with some refurbishment or personal alterations, but it supports the history and continuity of the monarchy (I’m not a royalist, but something of a historical buff).
If any are interested, this fellow has had a series of videos covering elements of the regalia and ceremony of the coronation. He discusses much of the history and traditions which go back to the Confessor. He also has videos visiting historical churches and their architecture which I find interesting.
https://www.youtube.com/@allanbarton
They probably figure that the times call for the most traditional pomp and ceremony possible to resurrect the royal identity among the people.
And anointing oil from olive trees on the Mount of Olives in Jerusalem, and the Stone of Scone, which was once thought to have Biblical origin.