Getting kicked in the shins is better than a bat to the skull. Would you be surprised when people start looking for alternatives when offered that "choice"?
The options were to spend 35 years in jail or to spend 6 months + plead guilty.
Are you saying that he chose to kill himself rather than spend 6 months in jail?
I don't know what went through his mind... but I think it's unlikely that he considered the plea bargain an option.
From what I've read, he seems like an idealist and in his mind it was probably more black and white - he had to plead plead innocent and accept 35 years or at minimum the financial and emotional damage that goes with fighting it... and he was getting little or no help from the world he was trying to change.
I believe the sticking point was being labeled a felon, not the jail time. Being a felon in the US is a Big Deal, and pretty much relegates you to permanent lower-classes [0]. Aaron also seemed big on moral integrity, and it's probably hard to reconcile admitting guilt to something you don't believe is morally wrong. "Live free or die" is a phrase with deep roots in our nation's history, for example.
The consequences convicted felons face in most states include:
Disenfranchisement (which the Supreme Court interpreted to be permitted by the Fourteenth Amendment)
Exclusion from obtaining certain licenses, such as a visa, or professional licenses required in order to legally operate (making many vocations off-limits to felons)
Exclusion from purchase and possession of firearms, ammunition and body armor
Ineligibility for serving on a jury
Ineligibility for government assistance or welfare, including being barred from federally funded housing