They probably look at their market share and decide they're not a monopoly anymore.
Unfortunately the US kind of has forgotten. The Bush administration took power and undermined all that anti-trust stuff and it lay forgotten for most of 20 years. The Biden administration is picking up some of it now.
except now the US' will to prosecute antitrust is essentially dead
the land of corporate power
Honestly its will wasn't even that strong back then, hence the slap on the wrist settlement on appeal.