Like if Rose got bubbled that wouldnt have stopped the gems from trying to save her.

But if your leader is dead and your army's entire system is based around you and only you being alive, chances are the rest of them gonna call it quits.

Probably why they tried to corrupt all the gems on the planet and left it to become a weapon.

Only justifiable way I see is if somehow owning a planet for a Diamond is more than just saying "yeah, that's mine." And it gives her some kind of power over it.