Just to be clear, MEGA didn't cheat and didn't have any arranged wars. Now that's clarified, I would like to clarify that the age following the MEGA age, the admins killed any way to reproduce that kind of kingdoms by:
1) Removing kingdom's based explore pool.
2) Limiting WW bonus gains on kingdoms with less provinces.
3) Increasing the penalty to explore for kingdom under 5 provinces to under 10 (iirc)
I haven't followed the whole "force merged small kingdoms" drama, but it's highly unlikely that this change was to kill something that was already dead.
PS They didn't remove #1 because of MEGA