If Ibarra pleaded guilty and the judge sentenced him, then the judge did find him guilty.
5 years for killing someone while DWI is not surprising. I have seen anywhere from 3 to 12 years for similar offenses(just off the top of my head). In a plea, the judge does not always review all of the facts before pronouncing sentence. The defense attorney and prosecutor negotiate the terms of the plea. The judge either accepts it or rejects it. In this case, the judge accepted the plea agreement. This does not mean that the judge would not have given a much higher sentence after a trial where there was no plea bargain agreement. Judge Smith is a rather conservative judge, and I suspect that if it was solely up to him, he would give a rather hefty sentence.