What would Sessions have investigated?
The past? That which went before President Trump's inauguration?
Correct me here if I misread the beginning but I seem to recall that virtually All the Past (during and probably before Obama's terms) was protected by Pardons issued to central figures (that was kinda hinted at anyway back then).
Meaning that these personages would have to commit same or similar offences again beyond Pardon protection territory?
Therefore, these personages were tempted to give it another go (the carrots of hope placed before them?) DURING Trump Presidency. The plan or a sizeable part of it?