the message went completely over the heads of the people it needed to reach
You had a series of very cynical and deliberately manipulative media coverage of the film which tried to spin it as anything but a climate change movie. And then you had a bunch of "man on the street" pieces intended to make viewers appear stupid.
But the core theory of media influenced economic change is rooted in the idea that a movie can shift people from their profit motives. No oil executive is going to watch a slapstick comedy and decide to shift his business's core financial model because of a few jokes. No bank executives are going to divest from carbon emitting industries because some Hollywood starlets made fun of them. No senior member of political leadership is going to change how mining permits and environmental regulations are written because Adam McKay posted big numbers at the box office.
The Network didn't change how Americans consumed their news media. Soylent Green didn't cause Americans to reconsider our policies on factory farming. Jarhead didn't cause any military personal to exit Iraq or Afghanistan. The only movie that seems to have really moved the dial on public policy is Idiocracy, the inspiration behind Elon Musk and Peter Thiel's quest to get more IT people to fuck.
Americans love nothing more than to wallow in their own filth while pointing and laughing at their neighbors.
I am smart. You are dumb. That's why we're in this mess together.