Okay... um, I have a lot of problems with this analysis, as someone who has lived in the Chicago area for most of his life except for times when the service had me elsewhere.
Lightfoot was a terrible mayor, because she simply can't work with people. She alienated the city counsel, and couldn't get things done. That said, she ran into the insurmountable problems of Covid and the George Floyd riots... So I'm not sure that even a mayor with greater skill could have handled it.
Rahm was actually... a pretty good mayor. He achieved some major reform of the schools, did a lot of good with infrastructure. His downfall was that he tried to cover up the circumstances of the Laquan McDonald shooting. What sealed it for him is that after numerous delays, the trial of the officer responsible happened right in the middle of the 2019 campaign!
Richie was darned good mayor. It's why he got re-elected five times, and served even longer than his father. He improved the cities economy and actually did a lot to make the city more livable. The murder rate even went down on his watch.
Sawyer (or as we lovingly called him "Mayor Mumbles" was terrible by design. The white aldermanic block that opposed everything Harold Washington did backed him because he would be easier to control before Richie claimed his job.
Harold Washington was a pretty terrible mayor for a lot of the same reasons that Lightfoot was. He couldn't work with the city council. He finally had to get the courts to redraw the aldermanic map to give him a more friendly council, and then proceeded to keel over. One of the things I heard from cops at the time was that he had a heart attack snorting cocaine in his office, but it was covered up. I don't know if this is true, but it says a lot that the cops would spread this rumor because they hated him so much.