That arms dealer should be in prison for life.
Possibly. But, for better or worse, Viktor Bout was only sentenced to 25 years, and given the time he has already been in custody (both before and after trial), he was due to be released in 2029. So it shortens his sentence by under 7 years.
Brittney Griner was sentenced to 9 years in prison over drug charges. Did she break the law? Yes. But given the relatively small amounts involved and the crimes that she was charged with, it is quite possible that charges against her were excessive and at least partly political in nature.
Was it a good deal? Meh, hard to say. Bout shouldn't be released, but Griner shouldn't have been subject to possibly trumped up charges.