Under Florida Law, the 10-20-Life waiver of mandatory minimums is at the discretion of the prosecutor. Why is this not at the discretion of the judge and at the discretion of the prosecutor?
The short answer is that this is because the Florida legislature decided to do so.
Why would they do that?
Prosecutors are perceived to be more consistently in favor of "tough on crime policies" than judges, so allocating the authority to prosecutors makes it likely that waivers will be granted more sparingly.
Prosecutors have the authority to plea bargain and bring a lesser charge that doesn't have mandatory minimums in any case. So, the waiver provision merely formalizes the ability of prosecutors to do openly something that they could have done through the back door in any case.
This follows the pattern of many other states.