After crashing on the planet, Seven took charge of the situation, telling the other drones what to do. While they were disoriented and confused shortly after the crash, each lining up and saying "input failure", Seven was able to assess the situation and begin to implement emergency survival protocols, while the other drones remained sufficiently clueless that they didn't even know which way to go without instructions when Seven told them to evacuate the area and also had to tell them to set up the homing beacon. Why wasn't she discombobulated after the crash like the others? There isn't supposed to be any hierarchy in the Collective, apart from the queen, where one drone would be in command over other drones. My hypothesis is that in such emergency situations where a group of drones is separated from the hive mind, that survival protocols will put one drone in charge, almost like a temporary acting queen, to direct the others as to how to carry out those protocols. Seven was likely the drone put in charge simply because she'd been a drone the longest. If she'd not survived, one of the others would likely have been automatically elevated to that told, I'm guessing. Your thoughts?
As Riu riu chiu wrote, one of the drones - the less "discombobulated"- had to take control, to allow him/her (and the rest of his/her congeners or Collective) to survive in an unknown and maybe, hostile environment. And why Seven? Simply because 1) she was the least damaged, 2) she seemed to be - and that at an early age - the most brilliante (intellectually speaking) and the most strongest* (mentally speaking) of all, at least of this small group. This being, we found out from "Scorpion" - part 1 (3x26), where she was chosen by others from the Collective, to be their spokewoman after Janeway & Voyager crossed their path, that these qualities were profoundly inked in her -> it is not surprising that she was the favorite of the Borg Queen and Janeway treated like her surrogate daughter and even maybe, her equal in spite of Seven's youth. 3) she was a prominent character and this episode allowed us to know more about her past. * even if we found out in following seasons, that Seven could show empathy and sensibility at times -, which could be considered as weakness but fortunately -, so much the existence of new Collective (Voyager and her occupants) was not in danger!
Maybe there were other crashes or separations where Seven wasn't the one in charge, but we weren't shown those stories because they didn't star Seven. We saw this one because it did star Seven.
There was one time she mentioned she was separated and was paralyzed by fear so maybe she was temporarily separated another time.