I think it's a bit of a hyperbole to say people are abandoning those other platforms for Steemit. With all due respect, those platforms are so big that Steemit could drown in them without anyone noticing. Furthermore, most people moving to Steemit, at least to begin with, are cross-posting their content rather than just posting it in one place.
(I must admit I am not a fan of "Steemit is amazing!" to the level it is often displayed on Steemit. It feels like a pyramid scheme at times due to it.)
Why do I think Steemit is surging? I think the original impetus was because a new whale is buying in. And Steemit is actually a solid cryptocurrency, so a surge in it is helping others buy in.
I mean, yes, people buy Steemit to gain more visibility, but from what I've observed, most non-whales sell their SBD for said Steemit, rather than buy in with an external currency.
I agree there are some who are "cross-posting" as opposed to "abandoning" FB.
It may be hyperbole - used to make a very complicated situation easy to understand.
The underlying point does not change. People are arriving. Whether they abandoned FB or fell off the moon could be the subject a 300 page study, but at the end of the day, an investor wants to know the conclusion in a few short sentences.
I agree that much of the rise is driven by investors, (not whales though), who are anticipating an increase in demand later, commensurate with the rise in users.
I agree there's an increase in users.
What I want to see now is retention rates. It could be that the increase in users is "fake", as in, we keep getting new people faster than old people are leaving, but if the average user leaves after, say, 1-2 weeks, then in a couple of months, the numbers will either decline or go down. This is a situation that one can see in many "Free to play" games that employ "pay 2 win" strategies. Early on, they keep getting new users at a faster rate than they lose them, but it doesn't hold.
Now, I'm not saying this is the situation here, but it might be. Steemit's problem with scalability of rewards is something that might drive people out, even if they currently find the place palatable :-/ I think a hard fork will need to fix that problem somehow, at least, for the longevity of the platform.