Because indictments don't get handed down until they refuse to plead guilty to the grand jury.
If they think they can beat it, they'll plead not guilty and it goes to trial.
The defense doesn't get to see all the evidence until after the trial date is set.
They'll only bring enough to the grand jury to prove that charges are warranted.
Clinesmith plead guilty straight up as soon as he saw what was released at the grand jury.
Chances are the others will too... Because what they see there is usually always just a tiny portion of the evidence.
They don't see it all until the disclosure stage after the trial date is set.
That's why so many plead guilty in the first day of the trial too.