Looks like a lot of scaffolding on it, was that installed for permanent support du to ag or were they actively working on it?
It was going through an intense restoration project and the fire was probably an accident from that. But, at the same time France has had an average of 3 churches attacked by vandals per day for 3 years. So I wouldn't entirely rule out vandalism on this one.
https://www.breitbart.com/europe/2019/03/30/macrons-france-average-of-three-church-attacks-per-day/