dumb down, to
1. To make something less complex, nuanced, or intellectually challenging, typically in order to make the content more appealing or accessible to a wider audience. A noun or pronoun can be used between "dumb" and "down." The first film was a real exploration of the human psyche, but they dumbed down the second film into a generic horror film. I think there are ways we can make the story resonate with the audience without dumbing it down. I think we ought to dumb the play down a bit. After all, most of the people coming to see it won't have a PhD in drama.
2. To change a fictional character, as in a TV show or film series, to be or seem less intelligent than depicted previously. A noun or pronoun can be used between "dumb" and "down." They dumbed his character down in later seasons, turning him into a total goofball for cheap laughs.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
To simplify something excessively in order to make it suitable for a less educated or less sophisticated audience: The researchers dumbed down the report before releasing it to the public.
The American Heritage® Dictionary of Phrasal Verbs. Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
dumb down, to
To simplify or otherwise revise in order to appeal to someone of less education, taste, or intelligence. This slangy expression dates from the first half of the 1900s. Publishers Weekly used it in a review of The Business of Books by André Schiffrin: “. . . the attempt to appeal to the lowest common denominator of taste, which has, he says, led network television and movies in such depressing directions, has dumbed down publishing to an alarming degree” (Aug. 21, 2000).
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer