Agents of S.H.I.E.L.D. season 5 is essentially a mystery story. Coulson and his team have arrived in the aftermath of the world's destruction and must learn what terrible forces shattered the planet like an eggshell, so that they can go back in time and prevent the disaster from happening in the first place. There's just one problem: all records that might have explained how Earth was destroyed have been lost. The agents' sole guide has been Robin, the time-lost seer who experiences time out of sync. She's told Agent May how to save the world - but first, the team have to understand how it was destroyed in the first place.
So what can we say for certain? Little by little, Agents of S.H.I.E.L.D. season 5 has dropped some tantalizing hints.
Quake, Destroyer of Worlds
Time and again, the series has described Daisy as "Quake, Destroyer of Worlds." At first, though, it was easy to doubt that Daisy was actually responsible for the end of the world. Deke, who grew up hearing the legends of the True Believers, managed to rebuild the Framework. He put the pieces together, and concluded that Daisy was the one who ravaged the Earth.
Deke is hardly an impartial source, though. His childhood had left the con-man bitter and frustrated, and he viewed the legends of the True Believers as a foolish superstition. It would certainly be fitting for him to dig into the few historical records that remain, and conclude that one of the True Believers' heroes was actually a monster. What's more, Deke was experiencing history by recreating the Framework. It's very possible he was experienced a twisted, distorted version of reality, in which Daisy had actually been a member of Hydra.
Deke's views were apparently confirmed by Kasius. Although Kasius had done his level-best to erase all knowledge of Earth's history, he clearly believes Quake to be the "Destroyer of Worlds" as well. At the same time, Kasius is no scientist. He's driven by petty ambition, and wants Daisy as his prize. He hasn't stopped to consider the fact that time appears to be in a loop, with the twenty-first century and his present day feeding into one another. Matters of science, philosophy, and temporal physics are of no interest to the Kree aristocrat. It's doubtful that he cares much about history; the most likely reason he wiped out humanity's historical records was to try to end any movements that preached a message of hope. So, again, Kasius shouldn't be viewed as a reliable source.
Gravitonium is Back in Play
The next clue has been the return of a concept from Agents of S.H.I.E.L.D. season 1 - the fictional element known as gravitonium. In the episode 'Together or Not at All,' the S.H.I.E.L.D. team discovered that gravitonium was used to generate the Lighthouse's artificial gravity. Showrunner Jed Whedon has always promised that this concept would be revisited sooner or later, and it seems that now is the time.
Fans immediately theorized that gravitonium was somehow involved in the Earth's destruction. That's apparently been confirmed in the last two episodes, which revealed that gravity is in flux around the shattered Earth. The surface is subject to devastating "gravity storms," random gravitational fluctuations that can be fatal to anyone caught up in them. Only gravitonium could possibly cause that kind of phenomenon.
Daisy doesn't have the power to destroy a planet. But if her powers interacted with gravitonium, anything could happen.