Hello T. A. Gardner
Because if something chargeable were found he'd already be indicted. I have no illusions about how hard various groups want to get Trump. The "fishing expeditions" to do so abound. If they really had something, Trump would be charged in a nanosecond with it.
Why do you believe that? Could it be that there are other possibilities besides this assumption? What could those possibilities be?
It is not best practice for a DA to always immediately charge a suspect with a crime as soon as evidence of it is first uncovered. That could compromise further investigation. If investigators believe there is more to be uncovered it is often in their interest to keep a lid on whatever they have discovered to date.
One method which is frequently used is to charge people lower in the echelon of an organization in order to get them to talk about what they know. Serious charges and the threat of doing time often leads to more information about those higher up in an organization. Let us also realize that these things take time. Someone may not fully grasp everything they are facing until they have time to think about it. They may try to divulge just enough to get them off the bigger hook, while still holding back good actionable information.
Trump Org. and top aide charged with 15-year scheme to defraud U.S. of taxes
"Prosecutors described a conspiracy to compensate executives "off the books" to avoid paying taxes.
The Trump Organization and its chief financial officer, Allen Weisselberg, were charged Thursday in what prosecutors said was a sweeping, 15-year scheme to compensate top executives of former President Donald Trump's company “off the books” and help them avoid paying taxes.
The Trump Organization pleaded not guilty to charges that included tax fraud and falsifying business records. Weisselberg, 73, pleaded not guilty to grand larceny and tax fraud charges, among others, after prosecutors accused him of personally avoiding taxes on $1.7 million of his income."
Nobody really thinks for a second that Weisselberg isn't guilty of more than he is being charged with. He's already looking at doing hard time. Investigators are undoubtedly uncovering more as time passes. They could approach Weisselberg with an offer he'd have a hard time refusing: "Either you cooperate fully, or you're looking at the rest of your life in prison." That could lead to Weisselberg talking. But, of course, it's not like it would be just one discussion. Investigators need time to check out the things Weisselberg may have told them. They need to verify if it is true, and if there is more to it. It could be a situation of checking out the spilled beans, and then finding that there are more beans in the bowl. They might have to have another discussion with him. Remind him of what he is facing. Up the ante.
I'm sure they are quite adept at what they do.
And I would be surprised if they would make whatever they may have learned already a public circus as soon as they learn it.