how does pangloss' philosophy backfire on him and on cunegonde?

"Dr. Pangloss and his philosophy are the principal focus of Voltaire’s satire. Dr. Pangloss, Candide’s tutor and mentor, teaches that in this best of all possible worlds, everything happens out of absolute necessity, and that everything happens for the best." (1)

His philosophy backfires when he finds he's contracted syphilis Columbus' fault, but he also made chocolate possible) and Cunegonde is murdered by Bulgar soldiers. So much for everything happening for the bast!

"Best," excuse me!