The cluster, made up of shards that have been forced together, but what shards did they use to make the cluster, did the diamond authority shatter millions of there loyal subordinates to make it, I think not.
As we no longer see Pink Diamonds symbol on the spaceship in Jailbreak we can safetly assume she is no longer apart of the diamond authority anymore. It may very well be that the diamonds, after losing the war with Rose Quartz decided that Pink Diamond would have more defective gems from her ranks who would also rebel and pervert other gems. They could not have that so they decided to kill two birds with one stone, destroy the earth that Rose Quartz fought so hard to protect and at the same time get rid of a useless Diamond and her underlings. Below is a leaked picture of the cluster as you can see most of the gems are pink, but un-shattered, does this mean Pink Diamond and her followers are still alive, are they going to come back? With one more day till Steven Universe in to deep comes on, we will find out.