I don't normally do these kinds of theories. If you read my theories (if not you can find them in my profile page) you would know that I mostly theories of small trivial things like Garnets visor, Peridots ferrokinetisis or if Sapphire has a weapon. But I thought this was too good not to share. It's about who I think shattered Pink Diamond and why (and no, I don't think it was White Diamond)
Firstly let's start with what we know about PDs shattering.
We know that Eyeball witnessed Rose shattering her and that Garnet, Pearl and (presumably) Amethyst knew Rose had Shattered her. Presumably because (in Garnet and Pearls case) they saw her do it, or she told them afterwards.
But then came "The Trial" where Defending Zircon found holes in the story, namely the fact that Rose was able to get close enough to PD to shatter her. She assumes that the real culprit must be someone who PD trusted (specifically a Diamond).
However, DZs theory does have some holes. 1. Why did Eyeball say she witnessed Rose shatter PD? and 2. Why would Rose let her own teammates think she was the culprit?
Therefore, I think the mastermind behind the shattering was....
....Pink Diamond!
But wait LapisLazuliisthebest! How could that be?
(Spoilers for Harry Potter: Half blood prince and Deathly Hallows)
No PD didn't shatter herself, but rather she arranged for Rose to shatter her instead. I'm not saying that PD was on the CGs side. Far from it. Rose and PD were on opposing sides of couse.
This overlaps with two other theories. 1. Pink Diamond was newly made, possibly on Earth (hence haveing only one planet) 2. She didn't realy want to harm the planet.
If the theory that PD is fairly young is true then she would have been quite naive. It'ss possible that she didn't know she was harming Earth and the inhabitants. But when she realised her mistake she knew it was too late to convince the other Diamonds to end the war. She knew the only way to end it and make Homeworld leave was too be shaatered, So she arranged Rose Quartez to assasinate her and end the war.
Like the record goes "Pink had just stepped out and had only taken a few steps forward when Rose attacked her from the front!" and this is how. because Pink and Rose had planed it themselves.
Eyeball would have seen this like how Harry would have seen Snape killing Dumbeldore in "Half Blood Prince". It looked like a cold blooded murder when in reality the "victim" was sacrafice their own life for the greater good by asking someone else to kill them.
What do you think?