When the computer revolution got going, Apple was the biggest early success. A lot of people had really missed this technical revolution and missed out on investment opportunities. They didn't want to miss out on any more aspects to the growth of this new business. So funding of companies with products in the computer area was very successful and very abundant from some point on. Well, for one thing, they all started with certain types of engineers that were already omnipresent here.
Companies find it easier to expand than open offices in other states.
Venture capitalists value closeness to the rest of this fantastic business climate. New companies can always find tons of engineers already here. A company that makes a graphics board has trained engineers in the art and sometimes they will start a new graphics board company, or go with one. So you can see a lot of reasons why an industry would tend to be lumped into groups, like traffic on a highway, or swarms of bees, or flocks of birds. I was not anything close to the father of the Macintosh paradigm.