How is Liesel's stealing of a second book a pivotal point in what is to come in The Book Thief by Markus Zusak?

The section entitled "A Girl Made of Darkness" is found in Part Two of Zusak's The Book Thief. It gives an explanation of events that occur after Liesel steals her second book at the Furor's birthday bonfire. Two major events happen as a result of Liesel's thievery: the mayor's wife, Ilsa Hermann, witnesses the crime; and when Hans Hubermann discovers the stolen book, he gets an idea that will help to save a Jew's life. The narrator explains it as follows:

The act of stealing it triggered the crux of what was to come. It would provide her (Liesel) with a venue for continued book thievery. It would inspire Hans Hubermann to come up with a plan to help the Jewish fist fighter. And it would show me, once again, that one opportunity leads directly to another (83).

The "venue for continued book thievery" refers to Ilsa Hermann's private library. Because Frau Hermann sees Liesel steal a book from the bonfire, she later invites the girl to visit her library and read her books. Unfortunately, after Frau Hermann stops employing Liesel's mother to wash her laundry, Liesel screams at her and eventually resorts to stealing books from the Hermanns' library. The relationship between Frau Hermann and Liesel doesn't end there, though. If Frau Hermann had not seen Liesel take the book that day, then she never would have invited her to her house to read. If Liesel had never read in Frau Hermann's library, she might not have developed a relationship with her. Because Frau Hermann and Liesel develop a relationship in the library, the mayor's wife eventually takes Liesel into her home after the Hubermanns die.
As far as Hans Hubermann's "plan to help the Jewish fist fighter" is concerned, the stolen book from the bonfire gives him the idea that Max Vandenburg would probably be able to travel to Himmel Street undetected as a Jew if he were always found by people reading Mein Kampf—Hitler's autobiography. This book was required reading material for Nazi supporters; therefore, if Max were found reading the book while he traveled to the Hubermann's house, then he might just make it there alive. The plan works, and Liesel is blessed to enjoy Max's company and to build a loving friendship with him that continues after the war.