> But if you have say 100 billion, why put it into "yet another collider" rather than say condensed matter physics and quantum information research?
Because the only reason you have $100 billion to spend is that it's a large scale infrastructure project. And that money is trickling down to member states through contracts to a mix of businesses who hire white and blue collar workers.
It is equal part economic stimulus, political marketing and scientific research.
You can't just ask for the last part and ignore the first two.