Even though the show isn't entirely accurate, the "delusion" and "naivety" are rooted in reality. Therapists testified that Lyle and Erik's mental capacity was like that of 8-10 year olds at the time of the crime. The abuse and financial control from their parents made them completely dependent and severely distorted their view of the world. So, the case is not as simple as saying, "They were 18 and 21, they should have been mature adults about the situation". They weren't capable of handling it in a "better way".
Amazing comment! I 100% agree with what you are saying. In fact, in our review of episode 5 that comes out today at 3pm, we echo that exact fact. Physical age and emotional age are two different things and both brothers were definitely not operating on a level where their emotional age and physical ages were equal. Again thanks so much for your comment! Would be honored to have you as a sub and frequent commenter on our channel!