Will watch this thread to learn more. I may be wrong, but I seem to recall that there are numerous other collidors smashing atoms (probably the same atoms). But the size of this one is to allow us to “see” the smallest particles or something. (Although I imagine in 20 years we will need a bigger one, because after all our study we will have discovered that there must be something even smaller!)
That's what everybody thought until they tried it and the hadrons kept getting bigger