You're mixing up evil--for example, humans who choose to murder other humans--with nature. An earthquake isn't a product of an evil force. It's a product of shifting tectonic plates. A cholera outbreak is a consequence of political decisions made a long time ago, combined with the destruction of infrastructure in an extremely poor country. The view that everything which happens is a consequence of a struggle between good and evil like the one between God and Satan in the book of Job, or like the good guys and bad guys in an old-fashioned western, is one of the more ridiculous aspects of Christian thought.
Christians and atheists frequently share an interest in discussions of ethics and purpose. When you start with the assumption that God exists, everything stems from that assumption. A blogger I formerly read, Sprittibee, railed against the HPV vaccination (which would imply that her daughter or her daughter's life partner might have sex with another person--since that would never happen, why would her daughter need to be vaccinated?). The HPV vaccination was an example of our un-Godly culture (e.g., people have sex outside of marriage), not a medical advance that could save lives. At the same time, she asked us to pray for a child who received a heart transplant. The transplant took place in a hospital, and the child spent his last hours in that medical facility. When the child died, the discussion was all about God's will and how the child was now in heaven ("God took the child home). No one mentioned the role of medical science in the heart transplant. The doctors weren't praised or blamed. I was surprised, though, that these Christians would reject one medical advance because it was viewed as an assault on Christian ethics while they embraced the other. A devout believer would say, "God led those men to develop heart transplants" so does that mean Satan led doctors to develop the HPV vaccine? But the HPV vaccine can save lives, so is it really the product of Satan? So God is responsible for everything that happens, from a child dying in a hospital to Ted Bundy to cholera in Haiti to earthquakes in Christchurch--no, you silly atheist, that's not God. Those things are bad, so that's Satan. But God made everything? Yes, everything. And God created Satan, and thereby evil. Well, no, the Christian says, Satan chose to disobey God. You're forgetting free will. Men can choose to believe and follow God, or they can follow Satan. Right. Whatever. You've lost me.
I can understand the need to explain what happens on our planet and in our lives. I still wonder why my father developed chronic lymphocytic leukemia. Was it because we were in the fallout path of the above-ground nuclear testing in Nevada? Was it because he worked in a molybdenum mine? Maybe he contracted it because he prospected for uranium. He always blamed excessive x-rays given to him in the 1940s. He might have had a genetic predisposition to develop it since his first cousin also died from the same illness. I never thought, well, God has a mysterious plan for our lives, and it includes the need for some people to develop leukemia and die. I also never thought, well, leukemia is the work of Satan.
I read religious blogs, astonished by the hours and days and months people spend analyzing the Bible and trying to use it to explain their lives--scoffing at those of us who attempt to remain rational. If you start from a faulty premise--i.e., God exists--you're going to spend a lifetime explaining away the inconsistencies of religious texts and making up silly theologies and exclaiming that you're right and the other guy is WRONG WRONG WRONG because he interprets things differently than you and how many Christian denominations are there in the U.S. anyway, each denomination expressing the RIGHT interpretation?
Everything makes more sense when you start from the premise that God doesn't exist.