I think the speed of a Bjjer's game varies from player to player.
Generally larger Bjj player's are going to have a much slower game whereas the smaller ones are going to have a much faster game when compare to each other.
I think the same can be said about Judo.
I think when comparing Judo to Bjj in regards to the speed of the game I think judo is faster partly because of the rules but also Judo, as well all know, has a strong emphasis on the standup game and standup, if it is effective can't really be done slowly.
This is true for boxing, wrestling, muay thai. Any martial art that involves fighting from the standup position must involve some speed of movement.
Generally fighting on the ground is much much slower than fighting standing uo ALTHOUGH I've seen some bjj competitors who have a very fast pace ground game (but their speed on the ground still doesn't much the speed needed for standup in my opinion).
Shaolin Riberio, Leo Viera, and even Dan Camarillo are some Bjj competitors that have a fast pace game. Even though Dan is also a Judo player I think the reason why his game is fast is most because of his physical size and agility. If you have a body type built for speed and the coordination (and dexterity) to move and change position easily and quickly then I think you'll naturally have a game which leans toward speed.