Microsoft was in a position to put Google entirely out of business at the time, and buy it for pennies on the dollar. Internet Explorer was THE dominant browser at the time with over 90 percent market share, and Microsoft was considering blocking the install of Google Toolbar (the vaguely malware-esque add-on Google paid Adobe to inject into Flash Player and Reader installers) and preventing Google from modifying the default search.

Google would not still exist without the antitrust lawsuit against Microsoft that scared them into playing it safe.

Also, Larry and Sergey's vision was an academic search engine that wasn't tainted by the mixed motivations of advertising[1]. Since they built the world's largest ad company, it's fair to say they sold out their vision and mission and the first opportunity for a lot of money.

[1] http://infolab.stanford.edu/~backrub/google.html appendix A

Well, they had a clear vision about "organizing the world's information", but ads did not enter the picture until year 2000.

In 1998 they were decidedly anti-ad, but after failing to monetize differently, I guess they caved in.

However, that anti-ad approach and an attempt to avoid the results being gamed with PageRank made hordes of "us" (geeks who were being called in to help others with their "computer problems") to get everybody to switch to Google Search.

But I doubt they planned all of that, especially not to turn their company into an advertising company.