How did the stereotype Jews control the media develop?

[kaganate]

" I tried researching it, but all that does is bring up conspiracy sites with little to no factoids, and mostly personal ranting "

That's pretty much the standard of proof for this stuff.

I think the media thing developed kinda like this:

Until the Civil Rights laws of the 1960ies, Jews were kept out of a number of professions, professional associations, etc.
Vaudeville, movies, comics -- these were all seen as less than respectable and mostly "flash in the pan" activities which the Jews were not prevented entry to because the Anglos in charge did not think them worth bothering with.

'Course -- the Jews made them work
and a few impoverished bowery Yids became "the Moguls" of holywood

Then, once they made it, the Jew-haters saw that success as evidence of wrongdoing --
and - if there were Jews making movies - then they must be inapropriately controlling the media.

'course the reality is that even with the Jewish "Moguls" in charge, until very recently no Jewish actor could get a job if the Jewish identity was perceivable.
So -
Nathan Birnbaum became George Burns
Dave Kaminsky became Danny Kaye
Issur Danielovitch became Kirk Douglas
Betty Joan Perske became Lauren Bacall

Can you imagine how different American culture would have been where a marquee would have read:
"Spartacus starring Issur Danielovitch"
???


..and, of course, once a Jew-hater discovered that someone was a "secret Jew" -- then that served as further evidence of the great big plot.