Real creative humans don't tend to "create" "content". They write essays, sing, do sketch comedy, dance, take photographs, etc. This is a long-running peeve of mine but I'm bringing it up because the corporate language obscures the nature of this complaint.
Imagine: "I've read some really good plays, but it's not always obvious what's going on. Playwrights should write out prose between the pieces of dialogue so it's as easy for readers to understand as possible."
Anyone can see this would be silly, since the form--drama rather than prose--is part of the intended experience.
If you are consuming Twitter threads equivalently to long-form content, you are missing out on part of their value, since each tweet is open to its own replies. This means that people can chime in with their own stories or anecdotes or objections non-linearly.
Cory's thread doesn't do this because it's so long it breaks the Twitter UI's conventions of loading first the thread, then people's replies. I would cede that makes Cory's Twitter thread relatively ineffective.
However, it can still be the case that someone can excerpt via RT a particularly interesting detail they want to highlight without viewing an entire thread as worth the time.
So we get back to intent: some writers would hate that for sentences out of their blog posts. Some writers like to make that form of discourse part of what they're doing. (It's pretty common for a thread's author to further engage with replies to particular Tweets) If you don't engage with that, then yeah, of course it looks preferable to just copy-paste the text into a blog post to read. But that doesn't mean that people are mindlessly "forcing" each other onto a "bandwagon" because they "get a tonne of followers."
A reprehensibly techie comparison: If you don't use stuff like transclusion and non-linear structure, outliners seem like they just introduce noise into what could just be paragraphs of text. But... the whole point is the part you're not using.