I think this is something about the incentive structure of the US legal system.
Here in Australia, a member of my family was involved in a fatal accident with a pedestrian, around 20 years ago. They put him on trial even though the case was weak, and then the prosecutor moved for dismissal part way through the trial. But, what people told us, is prosecutors are encouraged to take weak cases to trial because dropping the case part way through the trial is more politically palatable than refusing to bring it to court to begin with.
Here in Australia, a member of my family was involved in a fatal accident with a pedestrian, around 20 years ago. They put him on trial even though the case was weak, and then the prosecutor moved for dismissal part way through the trial. But, what people told us, is prosecutors are encouraged to take weak cases to trial because dropping the case part way through the trial is more politically palatable than refusing to bring it to court to begin with.