What would be the benefit for him to buy Steem I do wonder?

Indeed this is a puzzle for me too.

And how do you take over a blockchain project? Do you buy steemit.inc?

So far the rumor is about buying Steemit, not Steem. But if you get Steemit, you get plenty of Steem to influence the blockchain...

Also do wonder if this would be good for steem or not!

Hard to answer as well. But, do you think it would be better if Facebook acquire Steemit?