President Biden's Antitrust leadership wants fewer mergers, but changing merger policy is hard when your decisions can be reviewed by a court and go against 50 years of well-developed case law (See Can the FTC Turn Back the Clock, written by some middling economists).
Instead, Biden's regulators are trying to change policy indirectly, by creating what Sokol et al. call "Regulatory Uncertainty,"which acts as a tax on mergers.
Surprisingly, however, practitioners thought that the harm might be limited:
As the FTC and DOJ continue to focus their attention on resource-intensive enforcement of a few high-profile technology and pharmaceutical companies, practitioners see more deals escaping scrutiny.
So basically, if President Biden's regulators are busy elsewhere, they cannot prevent as many mergers.