When did that ever happen? Can you think of any examples from the time period you are talking about?
When I was living in Chicago, several major politicians on the city and state level went to prison for crimes that are no longer crimes for their predecessors because they have legalized those behaviors.
"On Aug. 14, former Illinois Congressman Jesse Jackson Jr. and his wife, former Chicago Ald. Sandi Jackson, were sentenced to 30 months and 12 months in prison, respectively, for charges related to their spending of $750,000 in campaign contributions on personal expenses."
Now senators and congressmen are allowed to keep, spend, or otherwise do whatever they please with their campaign money.
See here
Also, 4 Illinois governors have been sent to prison ...
Rod Blagojevich was governor from 2002 until he was impeached on January 30, 2009. He was convicted of numerous corruption charges in 2011, including allegations he tried to sell or trade President Barack Obama's old Senate seat. He served nearly eight of a 14-year sentence at a federal prison in Colorado, before being commuted on February 18, 2020 by President Donald Trump.
George Ryan was governor from 1999 through 2003. After leaving office, Ryan was convicted of racketeering for actions as governor and secretary of state. In November 2007 he began serving a 6 1/2 year sentence in federal prison. He was released from home confinement on July 3, 2013.
Dan Walker served as governor from 1973 through 1977. He pleaded guilty to bank fraud and other charges in 1987 related to his business activities after leaving office. Walker spent about a year and a half in federal prison.
Otto Kerner was governor from 1961 through 1968. In 1973, he served three years in prison after being convicted of bribery related charges. Kerner was a respected judge at the time of his conviction.