You keep it unified because then you have a single entity to regulate. The problem with Facebook does not stem from a lack of market competition but rather its fundamental business model of allowing anyone to purchase ads.
If we are concerned about Facebook being used as a vector through which bad actors try to influence elections - which we should be - then we keep it unified and regulate it so that ad purchasers must be vetted and approved, especially if the content of their ads relates to politics.
You keep it unified because then you have a single entity to regulate. The problem with Facebook does not stem from a lack of market competition but rather its fundamental business model of allowing anyone to purchase ads.
If we are concerned about Facebook being used as a vector through which bad actors try to influence elections - which we should be - then we keep it unified and regulate it so that ad purchasers must be vetted and approved, especially if the content of their ads relates to politics.