Continuity mistake: When Peter is having his vision of New York, D.L. can be seen picking up Micah and running away. When the camera pans out to show Matt holding them back, D.L. is picking up Micah again.
Continuity mistake: In previous episodes, when we see DL getting into the car as Nikki prepares to shoot him, he pauses for a second and looks around. In this episode, when we see the actual shooting, DL never looks around, he just opens the car door and prepares to get in, without pause.
Chosen answer: Because he's an idiot. From the story point of view, they needed the vault to actually be physically open so that the release of the virus would be a credible threat. Unfortunately, this required that Peter conveniently forget that he could simply walk through The Wall and use his telekinesis to tear the door open instead. Peter's increasingly large arsenal of abilities, where he ended up having pretty much any ability required for any situation, led to a situation where it became necessary to either have Peter apparently forget that he had a given power, as with the vault door scene, or become naively trusting, as with his refusal to scan Adam's mind to confirm his good intent. This problem, which simply made Peter look increasingly dumb as the show progressed, may well have been a key factor in the decision to severely reduce his ability during season three.
Tailkinker ★