Funnily enough Hotmail which was the premiere email service when GMail launched didn't have any meaningful increase in storage until like 10 years later
And instead of the same enthusiastic reaction at large they had become used to, they got _hammered_ for it by publishers and dragged into court. I do wonder if that turned into a fundamental cultural inflection point for them.
Same year they introduced Android, another decent success.
You could load to IFrame (but then have to rewrite it in IE for some reason, NS was fine with that - if knowing a way to avoid that layout flush bug after resize..) years before that, as I did.
In my opinion XMLHttpRequest made more damage than help by forcing JS as the only way of doing similar things instead of letting bugs that what was there already to be fixed - so now, you can not even imagine, I guess, how all that could be different - mostly without need of JS and browser able to handle it..