If you learnt to build a browser in 2000 you're probably doing well for yourself lol.
Not a lot of demand, but also probably not a lot of supply.
For this example, if you built a browser in 2000 it would put you in a great position to launch android in 2008. I think this is pg’s point. You spend all this time learning the interesting bits and when an inflection comes along that makes a new product or service possible you could be the one to likely launch it
There is an entire graveyward of browsers, almost all that didn't die are now forgotten.