The Elite
BOSS
I'm surprised at how many people didn't understand the episode's ending, I felt it was pretty clearly laid out. The issue I think is that it didn't seem like an episode of Doctor Who, more like an episode of Inside No. 9 or similar, where it's a little self contained, slightly unsettling spooky story. The footage of the episode, in universe, has been put together specifically to get us to watch it and spread the infection, which is housed in the static. Reese Sheersmith's character is playing with horror/suspense tropes to create a story, something that people will want to watch. He's engineering these story beats to drive up tension and keep people watching. The whole episode is very deliberately from outside of The Doctor's perspective, playing with him not understanding what happened, and he's just distracted and outwitted by the bad guy, as are we. His confusion at the end is him knowing that something's not right, but being pushed off the station leading to him having to abandon what's happening without getting to the true nature of the infection.
Ok, that's sort of the way I interpreted it. I felt just as confused as The Doctor by the end though.
I had a hard time buying into the monster's origins in the first place.