And frankly, given his public comments about and noted vitriol towards Lina Khan and the FTC (and his own tendencies towards seeking monopolies) I assume at some point he'll try.
Further, purely speculating: it may be he already has tried. It's indicative that we didn't immediately see him go for the FTC. He's too small of a man to not have wanted to for personal reasons, and too greedy to not have wanted to for long-term business reasons. I have to wonder if he was restrained from doing so on account of (correctly) predicted blowback from such an action.
Seeming to come down on the side of John Deere and DuPont subsidiaries and spinoffs is not a smart move. These are hot issues for the populist wing of the party who want to purge what they label as the "Con(servative) Inc" wing and routinely make hobbyhorses of issues affecting farmers in flyover states.