Social media organic reach is very dependent on the social media algorithms. The algorithm determines what every user sees on their timeline. And that’s why it’s key to understand how the algorithms work so as to maximize your organic reach.
The algorithm is ever-changing, always improving to make sure that users see what they want to see most. For example, in the first half of 2018 alone, Facebook reported five major changes to the News Feed (and there are probably many more small tweaks that were not reported).
So how does each of the social media algorithms work?
Full article: How to (Still) Get Organic Reach on Social Media