The spire was made of wood.
Due to France’s laws regarding secularization, the French government owns all churches built before 1905, including Notre-Dame. The government lets the Archdiocese of Paris use the building for free, and will continue to do so in perpetuity. The Archdiocese of Paris is responsible for the upkeep of the church, as well as for paying employees.
https://www.catholicnewsagency.com/news/5-things-to-know-about-the-cathedral-of-notre-dame-in-paris-11196