WoT relays work because not everyone uses them uniformly. 

Suppose of the 1500 people I follow, only 1 of them use public relays and follow new users.

That automatically means the entire network of 50,000 (my 1500 follows + their follows) can now see these new users with just 1 follow.

Then multiply that by using 10 WoT relays, you will find plenty of people adding new people to the WoT organically