First off, I should note that just a day before the actual fire began a visiting lecturer named George Francis Train visited the city and issued a warning to the residents of Chicago that "A terrible calamity is impending over the city of Chicago". This warning was in regards to the poorly constructed buildings and homes hastily built all over the city and the constantly present danger of fire. The city, ignoring Train's warning, ridiculed him instead.
People present within the O'Leary household offered a different version of how the fire began, saying that there was a party taking place celebrating the arrival of some newcomers from Ireland. Philip Michael Kane, a child of one of the men present at the party, claims that his father carelessly emptied the ashes from his pipe on the floor of the barn which ignited the blaze.
After the fire was finished, the city of Chicago, including the Chicago Tribune, investigated the O'Leary home and described the family and the surrounding area as despicable. Due to the unrelenting humiliation delivered by the city, Mrs. O'Leary, often referred to as a "hag" and "crone", and the kids moved to a home on Wallace St. on the outskirts of Chicago. Sadly, Mrs. O'Leary was forced to face the scorn of the city until her death caused by pneumonia in 1895 despite a Chicago Tribune writer in 1893 admitting that he had fabricated the story to make it "colorful".
One of O'Leary's sons, Con O'Leary, grew up and eventually murdered a woman and maimed his sister after a long night of drinking, and the other, James O'Leary, eventually became the gambling and crime boss of the Stockyards District at 4183 S. Halsted St.
As for the infamous O'Leary cow, she was lost during the fire but later recovered. O'Leary sold the cow to a man named Schick at 15th and Morgan and the sister of the cow, "Dudley", was sold to a "Paddy" Sexton at 28 Waller St. "Dudley's" death was eventually reported in the Chicago press in 1890.
In my opinion, regardless of how the fire actually began, the city of Chicago was done a favor by whoever or whatever caused the Chicago Fire. Without its destruction, Daniel Burnham and the other famous architects of the time would not have been able to create the marvelous city in which we now live.