Involuntary manslaughter (no "intent" to kill) is a felony and subject to 2,3,4, years in prison. I suspect Missouri law is similar. More likely than not there were negotiations in Little's case between the D.A. and Little's counsel. There was also substantial background checks into Little in order to establish his solid life and other things that the probation dept would have to consider before their recommendation in court. Character establishment is critical and his attorneys did a good job to convince both the probation dept and judge that this was very likely a one-off situation. Then again there may have been some factual issues faced by the prosecution such as careful preservation of the blood sample to prove the high blood alcohol, possible contributing driving negligence by the deceased, etc. I could be wrong but I believe he was found guilty by a jury meaning the defense counsel thought enough of the case to take it to trial. Again I don't recall. In any event lots can go into a case before resolution that can affect the outcome after charges are initially made.