Data-gathering companies can and do co-operate, or someone wanting to learn something can just buy the data from several of them - price per bit of data should be the same. So breaking them up isn't really a solution to this problem.
As for why monopolies aren't getting broken up, I'd say a combination of increased corporate control of government, and global trade necessitating ever larger companies to compete, because tariffs are 'evil'.
As for why monopolies aren't getting broken up, I'd say a combination of increased corporate control of government, and global trade necessitating ever larger companies to compete, because tariffs are 'evil'.