Who says that "financial reasoning" trumps other concerns, like privacy, accessibility, or human rights? Reducing everything to financial gain/loss analysis may sound nice in your Accounting 101 class, but in the real world people exist.
Even the CMA's statement is focusing solely on competition concerns.
I'm not dismissing any other potential concerns that may arise from this, but I fail to see how this isn't just a case of "FB bad so let's fuck with FB".
Someone already mentioned it here, but why didn't Google's acquisition of Tenor received similar scrutiny? Just to be clear, I'm not arguing in favor of FB or anyone. My argument is against governments disrupting free market through unfalsifiable hypotheses of how an acquisition is gonna unwind and impact the competive landscape.
In this particular case it's clear to me that financial reasoning is needed to force the reversal of an acquisition.
Google didn't try control competition by locking down tenor.