Stormtroopers aren’t at the bottom though. We don’t really see them in the movies, but the imperial soldiers were the bottom. The intent behind the original trilogy was that Stormtroopers were the elite.

Uh, it didn’t all happen on the same day. One of Belinda’s first lines in “Lux” is “I slept in this,” referring to her clothes. This prompts the Doctor to change. But considering she slept, it doesn’t seem to have happened on the same day.