It is not common but it happens, and understanding how requires knowing what actually goes into a sentencing decision beyond the statutory maximum for the charged offense.
In Florida and most other states, the statutory maximum for a specific charge sets a ceiling for that individual count. But defendants are rarely sentenced on a single count in isolation. Multiple charges can be stacked, each carrying its own sentence, and those sentences can run consecutively rather than concurrently. Two consecutive life sentences on separate counts is legally distinct from a single charge exceeding its statutory maximum.
The other major factor is prior bad acts. At sentencing, a judge considers the defendant's full history, not just the current conviction. Prior investigations that went nowhere, allegations that were never prosecuted, depositions containing damaging facts, and any documented history of similar conduct can all be introduced through a Presentence Investigation Report and the government's Sentencing Memorandum. The prosecution files a memorandum recommending a sentence on the high end. The defense files one arguing for leniency. The judge weighs both and imposes whatever sentence they determine fits the totality of the circumstances.
Florida also has its own sentencing scoresheet system that can produce recommended sentences significantly higher than the statutory minimum for a single count when prior record and offense severity factors are calculated together.
If you believe the sentence was imposed in error or outside what the law permits, a direct appeal or a post-conviction motion challenging the sentence is the path forward. That requires an attorney who handles Florida criminal appeals.