I am not too sure because the article doesn't elaborate, but you can clearly see it has plateaued in a similar fashion to the Myspace trend. It's not just that, I see a general distaste for Facebook these days more and more, it's like it has gotten old and lost it's shine. I think even if people are not using Steemit or another platform they are just using Facebook less and less.
I believe Steemit will grow and we are still at early adoption phase, according to that pic there is less than 1 million users (Facebook has over 2 billion), many of which will not be using Steemit as their main platform..... yet.
You can look at the @acange blog here to see this report generated daily. 677K of those steemit users are considered to be dead accounts by his method of counting.
I count the people over minnow status as "mattering" since something like 90%+ of minnows give up after only a short time here. So that is less than 10K. We need many more than that to succeed here.
I'm definitely seeing people leave fb these days. They either announce if or are not posting if I go to their profiles.
Oh wow ok, lot's of inactive accounts on Steemit then, perhaps they are just lying dormant and many will fire up In the next bull run as word gets out and Facebook declines. It won't happen immediately but over a gradual time span.