Combine:

    * good peering all over the world
    * vast resources in datacenters to host it
    * minimum actual usage
    * the fact that it is not one of petabytes of videos that have to be stored somewhere, but a smallish content that fits in memory

and it's rather unsurprisng.

Wow, yeah, had to try after reading your comment - really is remarkable, it just starts. (And I didn't realise I would notice something faster than Youtube, which previously seemed fine.)