It's even worse than that really because one of the worst results is that people experience cognitive dissonance when you ask them critical thinking questions or show them information that doesn't jive with the narrative, cognitive dissonance is very psychologically uncomfortable so the result is that people feel severe psychological discomfort when anyone or anything challenges the narrative, which then leads to people actively avoiding any interaction or information that might trigger the cognitive dissonance (challenging the narrative). The tunnel vision as you describe it basically boils down to people trying to avoid severe psychological discomfort that they have been conditioned to experience if they think critically about nearly anything that involves the msm narrative. It's not even just people being too "dumb" it's like a psychological punishment system meant to discourage critical analysis.