Each of these segments is a platform with a different model for acquiring users, and each is also a platform with a different content format. The way you get views, the kinds of content that works, and the kind of content that’s possible are different. (Buzzfeed, of course, is amongst other things a machine for understanding and optimising for this environment.)
Within this proliferation, distribution models are moving towards both algorithmic feeds (Facebook, Twitter, Instagram) and manual curation (Snapchat Discover), and content models have on the one hand richer and more immersive formats (often delivered using video files) and on the other lighter-weight bandwidth-optimised text-based formats (AMP, Facebook Instant Articles). And though AMP and Stories are pitched on speed of loading, they’re also, like video on Facebok or Snapchat, under the control of the underlying platform owner.
That is, these models change how you get audience, what the audience sees, what you know about the audience and how you can make money from it. (And then, just to make life simple, something around a third of mobile web use actually happens as in-app views within Facebook.)
One could also suggest that this means video (including GIFs, or whatever format you want to add) acts as a new card format – a way to encapsulate any kind of content and let it travel, shareably, across the Internet. Embedding a GIF or video into a social network feed is, again, an alternative to HTML as a content delivery format, and again, you can embed anything you want, including ads.