The media has jack and shit to do with the decline of the Mainstream Churches into heresy and everything to do with leftist capture and corruption of academia in the early 20th century, well before mass media was even a major player.
You can trace the collapse of the Mainstream Churches directly back to the
Fundamentalist/Modernist split in American Christianity that began in the late 19th and culminated in the early 20th Century. This was primarily driven not by "media" consumption, but rather the relatively new fields of evolutionary biology and archeology, which were being used to call into question the accuracy of the Bible. American Christianity had two responses to this academic questioning, the first, by the Modernists, was to decree that much of the Bible that was previously understood as historical was actually "allegorical" and to deny that there was supernatural elements to it. This viewpoint, despite decades of further archeological study actually proving vast swaths of the Bible accurate to a further degree than any other ancient text, came to dominate academic including the major religious universities of the time. With this, the slippery slope down the slope towards atheism began at those institutions, which then churned out the next generation of pastors for those denominations... which further weakened the the Faith, which increased the atheism at those universities to the point where now most forget that places such as Yale and Harvard were founded as Divinity Schools and were explicitly Christian Religious Institutions for most of their existence.
The other reaction was that of the Fundamentalists, who took the opposite view, they decided to view the Bible as accurate, regardless of what science said, they would maintain the faith. These Fundamentalists were systematically driven out of the elite academia by the Modernists (much like how later Conservative and Moderate political voices have been systematically driven our by Leftists). These groups ended up forced into marginal denominations or founding their own Churches that ended up broadly collected into what is known as the modern Evangelical Movement.
Media, such as it was, had nothing at all to do with the origin or driving of the Modernist decay of the Church. It was driven by academia and elite academic acceptance and peer pressure, as Pastors, historically, were considered members of the academic elite and thus were susceptible to such influence, especially in their formative years in university from whence they would then go into the world and spread those ideas to their congregations.