If you haven't been keeping up with US antitrust litigation this year this would seem a little out of the blue, but the DoJ and FTC have been, at least comparatively, knocking it out of the park under Biden.
For more information, the term for the more corporation-friendly philosophy that's been dominant since roughly sometime in the 90s is the "Chicago School of economics". The Chicago School's ideas on antitrust are pretty ridiculous:
If a merger won't result in immediate price increases or output decreases, it is generally considered acceptable. There is little concern for long-term effects.
There is consideration for the intent of a merger. Lack of evidence of an intent to monopolize is given serious consideration in determining whether antitrust law applies.
The argument that mergers result in increased efficiency through scale is generally given more weight than concerns about market consolidation.
There is a general assumption that, if a company does become monopolistic, the market will self-correct. The idea is that new entrants to a market segment or other competitive forces will act as a natural corrective agent.
The Biden administration marks the beginning of a move away from the Chicago School. In particular, as far as I'm aware, Lina Khan (chair of the FTC) and Jonathan Kanter (head of the DoJ Antitrust Division) are very bullish on antitrust enforcement. One recent example of the progress was the ban on non-competes by the FTC, which indirectly acts as an antitrust measure.
Edit:
You can see from my outline of Chicago School antitrust philosophy that it's inherently contradictory. There's an emphasis on allowing mergers, but there's also a belief that market entrants will stop monopolies. We've repeatedly seen over the past couple decades that, when a company tries to enter a monopolized market segment, the monopoly will merge with the entrant at any cost. It would be funny if it hadn't caused serious harm. See: grocery prices (especially in Canada with their duopoly).