It's because it lies in the plane of the Milky Way galaxy, and is dimmed to obscurity by all the dust in our galaxy - it's like trying to look out of room filled with smoke. But infrared light can travel through all that junk pretty well, so the view from NASA's Wide-field Infrared Survey Explorer (WISE) is unparalleled.
The galaxy is actually pretty amazing. You can just make out the spiral arms, narrow and long, making a giant S in the sky; those were not seen before WISE took a look. But the picture is dominated by the galaxy's core, which in infrared outshines the rest of the galaxy's light combined. At the nucleus of Circinus is a monster black hole, and matter is spiraling into it. As it does so, it heats up to fantastic temperatures, blasting out X-rays and other forms of energy. This radiation heats up the dust around it - most galaxies are littered with the stuff - which then reradiates that away in the infrared. If you look just outside the intense core, you'll see a ring of light: that's probably where a lot of stars are forming, which again creates more dust that can glow in the IR.
Observatories like WISE open up a new window on the Universe, giving us a view of the sky that we might have otherwise missed... even when something is almost literally right next door.