My point is that you can't compare a platform like reddit to a protocol like email.
While gmail and outlook are insanely big, how much of all email traffic do they handle? Sure, they are insanely big, but I doubt they are above 50%
On the other hand, how big is reddit compared to all other link aggregators?
I think it's pretty surely far above 50%.
Or how big is YouTube as a VOD platform?
I'm not advocating for discuit, but being like "they think federation can't build a mainstream platform, but look at email" is kind of missing the point.
Also email is the only example for federation. It's an outlier, mainly because it was one of the first things on the net. Everything else is platforms, unfortunately.