Ok, I've thought about this for awhile but never considered that it might actually be what's going on until now.
What if Dave was delusional this whole time and the 3D world was never actually real?
Ok, hear me out.
After the whole incident with his legs, Dave accidentally created Expunged and discovered an entirely different Reality, which can be referred to as the 3D Realm, 3D world, whatever you wanna call it. But what if the 3D Realm was not actually an existing thing, but rather something that his head created for him to remind him of the incident. Basically his own trauma forcing him to hallucinate things that aren't actually there. The only reason BF can also see it is because of either FNF logic or because of the fact that he somewhat understands Dave's trauma somehow, despite having not been there when his legs got blown off.
When he "turned 3D" at the festival, he actually froze up and just immediately stopped moving. Boyfriend tries to wake him up through a rap battle, which half of the crowd yelled at him for because in front of him was a paralyzed man and he's just standing there rapping against him. Bambi and Tristan are also yelling at Boyfriend, while Girlfriend just sits on the speakers and tries to calm everyone down because she's the only one who knows and understands what Boyfriend is trying to do. Which would kinda explain why everyone who attended the festival somehow agreed not to talk about the whole 3D thing, because they didn't see it with their own eyes.
What if Bambi tries to snap Dave out of his delusions by breaking phones that Dave give to him? He knows it's a stupid idea but it kinda works sometimes, which is why he keeps doing it. And Tristan also tries to snap him out of it by telling him things that Tristan knows Dave wouldn't approve of, whether it be a lie or something that actually happened. And as for Muko, he probably still feels guilty for being the cause of Dave's delusions so he doesn't talk with him much as they used to when they were lab partners.
