Where are you seeing this and why have the staffers concluded it was intentional?
https://www.reddit.com/r/The_Donald/comments/bdnd9a/three_days_ago_a_muslim_jihadis_in_paris_was/
https://www.reddit.com/r/The_Donald/comments/bdp3h9/no_coincidence_its_holy_week/
https://www.reddit.com/r/The_Donald/comments/bdpeeo/875_france_churches_attacked_just_last_year_why/
My guess is that they know it started in two places. If they had even 40 minutes in the building while it was on fire, I think they’d have a fairly decent sense of this.
If it did start in two places, it would take more belief than I can muster to hold that it was not intentional. One might not have absolute certainty, but one would have moral certainty, which is sufficient to act upon.