The difference is that Gmail was way better than its competitors at the time. The spam filter alone was a huge sell.
edit: the 1GB mailbox !
edit: the 1GB mailbox !
products have to make an appreciable difference in the bottom line
hotmail had that nice tie in with messenger, which was a huge plus
other emails had the ability to delete email
google tried to use email for ads which users found creepy
google had an invite system that made signing up difficult
etc etc
They pay Apple around $8 billion a year to be the default search. Apple has made more from Google in mobile than Google has made from Android.