Alan Dershowitz says --
"It's all about leverage. They're going after Manafort on something that apparently has nothing to do with Trump — years ago, his own business.... But what they're saying to him is 'we gotcha now, and we don't care about that, but if you can tell us something about Trump and the campaign and collusion, we'll give you a get out of jail card free So it's all about leverage. That's the way prosecutors work."
"If he has nothing to offer, he's just going to have to defend himself on these financial charges that have nothing to do with Trump. This shows the danger. Sometimes prosecutors can twist you not only into singing but into composing, into making something up against somebody. They're so desperate to make a deal. ... If you can get yourself out of trouble by turning somebody else in, a lawyer is going to help you try to do that.
"If he only gets Manafort, at least he has earned some of his money — the special prosecutor. And if he can turn it into somebody a little higher and a little higher and a little higher, the dominoes begin to fall. So it's a win-win strategy for prosecutors and, of course, it creates vulnerability for the target."