There is something to be said about virality even without an algorithm. I pay attention to posts that explode and ones that don't. People are still subject to being sucked in to certain writing styles, content, and presentation. And humans are always subject to incentives. I think the big accounts learned how to write in a way that brings in more attention. If a post is too long, people and their short attention spans may not read it. If it's too short, it doesn't convey enough information. There is a sweet spot that grabs attention and resonates with people.