Honestly, some of the smartest characters would fail perception checks because perception and intelligence are so different. I love characters who are secretly brilliant but completely oblivious to obvious things around them because they’re too deep in their own heads.
A lot of older stories used the monologue as a convenient way to explain the plot to the audience. Sometimes it’s theatrical, sometimes it feels artificial. Like you said with the Laura Croft examples, there are moments where the villain conveniently explains everything while the protagonist...
Sometimes the brain just stalls, especially when you put pressure on it. I've come to learn that creativity is not a straight line of constant brilliance. It really has it's moments sometimes. There are seasons where words arrive effortlessly, and seasons where they don't.