On the Internet, you can find a bunch of articles that address the question: "What affects the ultimate Social Media engagement metrics?". You will read about likes, coverage, comments, ER, ERR, and other metrics. But the point is that this is just a part of the truth...
If you attempt to compile a universal model that focuses on involvement as the ultimate indicator and some variables as drivers, then such a model would be incomplete and non-universal anyway. In fact, things are a lot more complicated than that. Just check it out:
• Theory: audience engagement is always converted into sales.
Practice: we experienced cases where an account made good sales with almost zero activity. And the opposite case: people clicked the "Like" button below the posts, left tons of comments, but still it brought no sales…