I begin to suspect this is not an accident, as it happened on Orthodox Easter.
I hate to be boring, but don't forget that real candles are used in traditional churches, especially on Easter. They cause a lot of fires. A Byzantine church near us recently finished replacing most of its roof and interior after a fire a year and a half ago that started with an altar boy setting down a candle in the wrong place.
Unless the fire investigators find evidence of probable arson (and in NYC, they're good), I'd say a candle is the likely cause.
By the way, I also believe it's more important that we use real candles in this life than that we eliminate all risk from this life.
Interesting point. Especially as then there were other fires in Orthodox churches, in other parts of the world.