I see what looks like an industrial era (or later) building in the background, as if we are looking at a few wild flowers growing in a parking lot. Then they get ignited without any direct source of heat apparent, almost as if a massive flash energy wave from...oh...a nuke? The fact that Bethesda might have said it's not about Fallout 4, might be a simple lie. Or, it might be like a previous poster said that it's not "technically" Fallout 4, perhaps its a prequel game around the time of the actual Great Burning? It's all speculation at this point, but I think it's served the purpose that Bethesda wanted, to get people talking and hyped about a new product from them. If that was the plan, mission accomplished.