'during sentencing, the judge did not hear details of Peet’s attack on Scott.'
Is likely why.
The problem is - if he goes to prison, he'll go to prison for a few weeks, months at most. Then what? He'll have spent that time in the gym, hanging around with 'proper criminals', learning the tricks of the trade, and likely ending up owing someone a favor.
The idea of keeping him on a suspended sentence would be because he's likely having to attend a programme designed to change his ways. Whilst this may be a complete waste of time (especially considering he's continuing to be thug), the Judge will be trying to give the guy a chance, before consigning him to a life of crime.