Did they even have crack back then?
Cervantes/Quixote was less central to the story than you might expect. The whole Sancho Panza relationship, the cornerstone of the books, was eclipsed by the Dulcinea thing. Dulcinea, played by a tavern slut played by a crazy prison slut, is Quixote's main foil here- which makes sense, because the musical has jettisoned all the satire and most of the comedy. She was rather splendidly haggish, shrieking and throwing things at people, and growling in a low, rough voice- very much the Spanish Inquisition corner crack whore. So yeah, it could be a bit much that she gets inevitably redeemed, but once you have your female lead rubbing a "knight's favor" in her armpits out of spite, you've won me over. Also, she got most of the best songs.
So, I could mention how this the musical is fundamentally untrue to the books, but that'd be unfair. And silly. I think the authors knew perfectly well that they were taking a crazy, multi-layered, hetero-explosive* satire and making it into a message play about dreaming the impossible dream against impossible odds. They weren't adapting the book, they were writing a musical about what that crazy old coot does to people. Against their better judgement. The end of the first book, I believe, has Quixote returing to sanity on his deathbed. The public wouldn't accept it, knock-offs sold like hotcakes, and Cervantes wrote a sequel. "That ending is bullcrap! Let him ride again! Let him ride forever! Sancho too!"
*So full of different kinds of things that it's like to bust.