Because no less an authority than Jennifer Granick said [1] that the conceivable range of a sentence would be from 15-21 months (though she said it could go higher, so I rounded up to 2-3 years), and she is decidedly on Aaron's side on this. In fact she ended her discussion of sentencing with "But Aaron could easily have come out to over a year in his guideline calculation.". Either way the sentence is in the end not up to the prosecutors, whether they wanted to "make an example of him" or not.
Now is a year is an easy sentence? Probably not, but it's certainly not a very hard sentence. Either way according to Dr. Lessig the sticking point for Aaron wasn't the length of the sentence, it was the 'felon' label.
All the other hurdles you've mentioned, all of them, are surmounted all the time by much lesser men than Aaron. Sometimes I think that Aaron might have actually started to believe the type of crap that gets slung around here on HN about how being a felon ends your life, and I wonder if that had any influence...
[1] http://cyberlaw.stanford.edu/blog/2013/01/towards-learning-l...