While it would have been tempting to simply have computers scan the images for changes, that's difficult with brown dwarfs. They tend to be faint, and it's all too easy for a machine to gloss over that info or spend too much time on useless data. Castro and crew not only detected something a computer would likely miss, they found a particularly faint brown dwarf -- it's possible that a full-time astronomer would have overlooked it.

You might see more discoveries like this in the future. Backyard Worlds is expected to continue for several more years, so there will be plenty of chances. And since you're searching through images, just about anyone with a keen eye can participate. NASA even suspects that there may be brown dwarves closer than the 4.2 light years between the Sun and Proxima Centauri. Humanity may have a fuller understanding of its cosmic neighborhood thanks to people working in their spare time.