The biblical answer: The book of Job directly addresses this question. The answer it gives is, essentially, it's not your place to question forces beyond your comprehension.

The secular answer: religious mythologies are imperfect and serve a function beyond being a literal or scientific explanation of life. They have to be taken as they are, flaws included, if you want to get any use out of them.

Both of these explanations are true in different ways. Ultimately, the answer doesn't matter as long as you have a guiding principle in life that keeps you on the right side of fate.