Then this could not be the reason they won—initially it was not the “ubiquity of gmail” as it was just new to the market and could not be synonymous with email.

Then this could not be the reason they won—initially it was not the “ubiquity of gmail” as it was just new to the market and could not be synonymous with email. They won by providing a good service for free with an ever-increasing capacity and iterating over features. Note that I’m not suggesting it was perfect or the best solution; plenty of questionable decisions made along the way (the way inbox was handled comes to mind)