"It's something that has clearly and intentionally been ramped up in about the last three years, and I am not sure why."
It seemed you'd know why, as the answer is pretty obvious: just like the media is trying to normalize homosexual couples (when they're not), they're also trying to normalize race-mixed couples (when they're not), to get you to believe that different races don't exist (when they do), just as they want you to think that gender/biological sex doesn't exist (when they do).
Now, homosexual couples aren't normal for obvious scientific reasons: no species can survive and continue if members of the opposite sex stop mating. I'm not saying non-hetero people should be ostracized, but I AM saying they shouldn't be normalized (and this is coming from a bisexual person).
As for race-mixed couples, that's just down to a preference thing. Most people decide to date someone of their own race, and there's nothing wrong with that. The media WANTS you to think there's something wrong with that, because they're convinced it's racist to do otherwise, but there's nothing wrong with that, and it's not racist.
What's the endgame you ask? Well, that's were we delve into conspiracy territory, the the most popular ones being population control, sterility, eugenics, dysgenics, etc. While all those sound like outlandish accusations that are extremely difficult to prove, honestly, why else would the media try to normalize things that, quite frankly, weren't considered normal for valid reasons? If you haven't done so already, read the books "1984" and "Brave New World", and you'll start to understand why such conspiracy theories are thrown out there. Hell, with the way the leftist media is acting lately, they seem to be pulling right from the pages of these books. Those books may also get you thinking about other things, such as how the Nazis and Commies came about, the push for socialist/globalized health care, censorship, revision of history, but I digress.