Supposedly this is part of how racketeering cases go. Those defendants who flip early get the best deals, basically little more than a slap on the wrist. The next ones get good deals but not quite as lenient, and so on. Because they’re not even the real target. The real win here is the “testify in future trials” part.
What the prosecution actually wants is to snowball a critical mass of the conspirators to all plead guilty and point their fingers at the holdouts, especially the kingpin. That’s how you collapse the whole racket.
If you don’t make them turn on one another then the criminal conspiracy club can hold together and protect each other with plausible and consistent lies. But when some of them start squawking “yep we did it all and here’s how”, the other crooks’ alibis start looking a whole lot less believable.