What may have driven advertisers to embrace the internet early on its development despite considerable uncertainty about audience size audience composition and cost effectiveness?

Keep in mind when the internet advertising boom hit it was the dot com's that were spending the majority of the advertising dollars. The Internet was being fueled by the venture capitalists, who were looking for the quick buck and big pay day. The reason why we had the "dot bomb" was because the dot coms finally ran out of money and the traditional advertisers were not willing to spend the big dollars.