Was that not because the GOP governor was about to do some hard time himself? And he figured a little street cred would do him some good behind the walls in Joliet?
Chickenpooper isn't quite in the same position...
Gov Ryan was about to go to prison for the "Licenses For Bribes" scandal. I don't recall that there was any evidence that he knew what was afoot, but it happened on his watch, and he was a Republican, so he was guilty.
The story regarding the death-row inmates is a little deeper. He didn't give them clemency. Rather, he commuted their sentences to life. This wasn't because of any anti-death-penalty belief on his part. A local law school had investigated some of the condemned prisoners' cases, and found quite a few miscarriages of justice. DNA testing (which had not been available when they were found guilty) proved that some of those on death row could not have committed the crimes.
The cops and prosecutors were shown to be either incompetent or corrupt (or both). The public lost faith in the ability of the Justice System to discern between innocent and guilty; so Ryan halted the executions.
Public comments made afterward by police and prosecutors did not help their public image. At least one prosecutor, when asked whether it bothered him that he had sent the wrong man to death row; stated, "We did our job. We convinced a jury that he was guilty".
Chilling.
Former Governor Ryan of Illinois was not imprisoned at Joliet (a state facility) but rather at a federal facility, because he was convicted of federal charges in a federal court.