These clouds look like they're moving fast and the photographer snapped the shot in time to get the contrast of the orange against the blue against the black silouhette of the trees. It doesn't look manipulated so I'm inclined to believe it is an honest moment of serendipity. I like it.
You have a very dramatic sky in this image. It completely overwhelms the foreground tree silhouettes. Getting closer to just one or two of the trees and allowing them just a little more prominent position in the frame might help. Their position in the frame would make all the difference in the world. You don't want to hide much of that beautiful sky. You want your silhouettes to become more a part of it. A little color adjustment of reds and yellows could make the sky even more dramatic.
Nice image but it isn't serendipity in what I understand it to mean. it may be for the photographer at the time to be there but the image on its own merits isn't serendipitous.
wonderful colors, good pov. The bottom right is a little unusual, but overall top 10. Unless you were waiting for this ideal shot, i would say this qualifies as serendipitous.