question from the ignorant

I see some forums/websites that are almost instantaneous when you click. Others, not so much. Would this be uncluttered layout, server size, or something else? The best example I've seen is accuratereloading.com.  it's owned by a uae prince and I'm guessing money is no object when it comes to his site and forums.
Not a suggestion,  I'm just curious why Saeed's site performs so well and others not so much.

May depend partly on how much it has to load. MeWe takes forever, and I'm assuming that's because it has so many different chats/groups going at the same time.