OP thought it was one too. To be be fair, it looked like one from afar.
I haven't been able to watch the video, but I've gathered from this thread that many people think it was a nuclear weapon because of a mushroom cloud. Which is funny, and absurd. There's nothing special about a nuclear weapon that makes a mushroom cloud. Any large, hot explosion will.
(I don't imagine there could be a cold explosion, adding "hot" is just a hint as to why mushroom clouds occur.)
And brightness certainly isn't a clue, either. Christ.