You bring up a good point about starting from the tech rather than the problem. Usually the advice from VCs is to start from the problem and iterate on the tech until you solve it. What was very fortunate for Google is that the tech translated into a great business problem. Open up any CS textbook and 'Search' is always a major section. It was also a great business because the problem is important, frequent, and had not been properly solved by the big players in the mid 90s.
"And then we realized that we had a querying tool..." (Page)