a. What was the motivation and goal of the content creator?
As it always is: Ratings. The Mercury Theater was competing against the more popular Edgar Bergen & Charlie McCarthy on NBC. Almost nobody listened to radio drama. The only reason they did that night was Bergen had an unknown singer, and some people decided to check out what was on CBS. They likely had no idea what was on at that time. And they tune in to hear a fairly realistic portrayal of an invasion from Mars. CBS had required the Mercury Theater interrupt with disclaimers to inform the audience it was a dramatization, but apparently some people missed it. This kind of dramatization was new to people at the time. The radio networks employed sound people who had worked in movies, so it sounded pretty good.
b. Why did the audience respond as they did? No common sense? Lack of critical thinking skill? Failure to cross-check information with multiple sources?
How would they cross-check? The internet? It didn't exist. TV wasn't available yet. People in the area traveled to Grover's Mill to see what was happening, and of course nothing was there. Even telephones were primitive, and not everyone had them. So they heard what they heard and jumped to conclusions. That kind of thing still happens today, even with all the resources people have.
a. What was the reach of the broadcast?
b. How do they actually know the number of people who reacted as popularized?
They had radio ratings at the time, and CBS was very active in measuring its audience, so that information was known.
But the actual listenership was exceeded by the people who read newspaper accounts the next day. Newspapers of course sought to discredit radio as a source for news, and this played into their narrative.
Keep in mind we were also on the eve of World War 2, and Europe was under siege.
Of course this led to the FCC instituting rules on news coverage and the use of the words "bulletin"
Lots of books on the subject. Here's one:
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