Alright, so basically we've got two possible methods for the manner in which pink diamond's end took place - she was either eliminated by rose quartz under the rebellion, or snuffed out from within homeworld itself, presumably by another diamond. Now, while the second theory seems more popular or plausible at the moment, the issue continues to remain that this theory makes little to no sense in terms of motivation. Yellow and blue clearly blame rose for the event with an intense fury, and steven's remaining entourage seems to adhere to this explanation as well. Of course, the only reason the second alternative is in place would be due to the combination of that zircon's argument during the trial coupled with yellow's reaction to it, however after watching jungle moon and then coming back to the trial, it's honestly quite clear to me what occurred, or at least what the show wants us to think occurred. Yellow becomes consistenly enraged over the course of zircon's argument, retaliating rather quickly after zircon questions the strength of pink's defenses and the general circumstances under which the murder took place. However, after the zircon outright accuses the both of them for the crime, yellow's disposition changes immensly - she returns to a collected, formal behaviour-set and lazily eliminates both zircons. This change in temperament, at least how I see it, suggests that yellow diamond was relieved by the accusation - perhaps in that it ruined the zircon's argument with clear traitorous content, or perhaps she had simply "gotten carried away" and completely missed the true explanation, jumping to an outrageous conclusion. In jungle moon, however, we get an incredible insight into the case by finally beholding pink and yellow's relationship - pink was juvenile and completely unprepared for any responsibility, while yellow seemed almost ashamed by their shared status, sharply pushing pink to act in the way she was made to. This theory seeks to state that while yellow was not directly responsible for pink diamond's demise, she indeed had a great part to play in the murder - that it was yellow's fault for leaving pink open to an attack by rose quartz, and yellow either blames herself - or knows that her fellow diamonds will blame her if they learn of her actions. In what we see of blue diamond from the answer, she seems to be nonchalantly resolute in her belief that the rebellion poses no threat, and it can be assumed that she took little interest in her retaliation against it, perhaps believing that it was simply a mark of pink's low experience. This lack of assistance or involvement on blue's part would also explain how intensely she mourns over pink's death AND how she doesn't seem known anything suggesting that yellow is related to pink's death, and completely leaving her out of the accussation. Essentially, we've not been given anywhere near the correct context in order to imagine what exactly yellow did, but we can infer from her actions in jungle moon and in the trial that yellow was punishing pink for allowing a rebellion to form within her colony, perhaps restricting her access to troops in preparation to bench pink from forming colonies once more. As this happened, somehow the rebellion that yellow and blue believed to be a worthless offense, existent only thanks to pink's pure incompetence, managed to shatter pink as yellow diamond demilitarized her. This demilitarization would've also had to be something personal - perhaps as an extra lesson by yellow to put pink in her place - something white and blue would've noticed due to their detachment from the whole issue. Yellow was tasked with destroying the rebellion, she took extra methods in order to humiliate the spoiled and unexperienced pink, and rose took her chance and shattered the latter. Yellow, then, was able to avoid blame for the incident thanks to the lack of interest on blue and white's side, and the three of them together corrupted the rebellion, as they'd now seen it was a much greater threat than originally imagined to be (that the diamonds believed the rebellion was meaningless would've also been a good explanation as to why they simply didn't just launch the corruption attack in the first place).
Short Version: Diamonds blamed rebellion on pink's lack of experience, blue and white let yellow take care of it and backed off after seeing for themselves that it was meaningless, yellow took extra measures to humilate pink, decided to demilitarize and suspend her from colonization as punishment for her inability to properly complete her job, rose quartz took the opportunity to shatter the defenseless pink as her armies were being confiscated (where were her pink diamond's attendants? Her agates? Her sapphires?), and yellow blames herself/thinks she could be blamed for the event, explains her suspicious behaviour during the trial and her quite apparent hatred for rose quartz (Her tendency to quickly jump towards shattering rose or the preserved quartzes could be a way of trying to shift the blame for her own purposes, to convince herself that it wasn't her fault - that'd actually make a pretty good story arc honestly).
Anyways, all of this could pretty easily become invalidated, since we're still pretty early in the case, so don't take any of this too seriously
