Is it? Facebook is trying to "take over" areas not at all related to social media in order to gain more data and could act as a loss-leader in the game developer space just in order to bolster market share in other areas. Preventing that seems to be better for consumers in general.
What the the US government is doing, I have no idea about, but they don't seem to care a lot about preventing huge companies from taking over entire markets, even those not related to their core business. Which already is hurting consumers, but the worst has yet to come.
Has that acquisition been approved? You’re implying that it has, but last I heard of it, it was being investigated by both the FTC and the CMA in the UK.