If these organisations like CMA really cared about the market and consumers, then they would lobby the government for making such mergers outright illegal (so it would saved tax payer money - no more silly investigations and room for potential under the table deals).
Furthermore they would lobby government to create laws ordering giants like Amazon or Google to split and even split subsidiaries like AWS.
These consolidations are edge cases of capitalism that have not been regulated. They create market distortions and exploitation.
Organisations like CMA are just a cheap plaster and symptom of poor / lack of regulation.