These girls didn't arrive to the X Factor together. They first auditioned as soloists and were later on put together as a group. They seemed to make a combination, so they created their own band and now have a really awesome song called "Wings."
It is amazing how the X Factor helps talented people become successful. All of the girls from Little Mix are very talented and they deserve all their success. They might not be very known now, but just hold on. If they keep making songs, I am sure they will even reach the top of the Billboard list. One Direction is another example. I am not a huge fan of them, but I do recognize that they have great voices and good songs and they have a bunch of fans after them.
Anyways, I hope you enjoyed Little Mix!