The aggression between african cichlids changes when you have a larger population. If you only have a few cichlids, the aggression is only focused on one or two fish resulting in a bully and a victim; as was the case in your experience. When you introduce more fish, the aggression gets spread out more evenly which basically means that there are no victimized fish.
In my tank, there is one big bully, you can see him in the 2nd to last picture, he is on the far left with the orange top fin, and you can see him in the last picture looking really grumpy with just his head poking out of a cave (beneath the yellow fish). He has always been a jerk and he will chase fish around, but because he hates everyone equally, there are no targets.
This is atleast how I have always understood it.