You could also say the next big tech startup will come from a random town around the world instead of Silicon Valley. But somehow the concentration of capital,

You could also say the next big tech startup will come from a random town around the world instead of Silicon Valley. But somehow the concentration of capital, expertise and opportunity in one place has a multiplier effect that makes Silicon Valley unreasonably effective at generating startups. Similarly, you are more likely to "hit the high notes" in research by concentrating effort in a few places. The alternative is lots of duplicated efforts that each don't quite achieve anything. This applies especially to medical research where the barriers to getting meaningful clinical results are sky high.