The classical "problem of evil" is one that has been around for millennia.In one way it can be seen as purely a philosophical or academic quandary that could somehow be solved with an appropriate philosophical insight and argument.We feel outrage, perhaps even anger, and we feel deeply incensed that any just universe could allow such an unjust and evil thing to happen.
In another sense, though, it is a more-than-academic question.
When the problem is encountered in one's personal life experience it often becomes an existential problem, i.e., a problem that affects one's whole life.
But at some point it may happen in a life that someone you love deeply and someone you know to be a good person (perhaps this person might even be you) has the tragic misfortune of having to undergo a great and undeserved suffering.
When you see that happen, when you watch that good person undergoing such enormous undeserved evil, it violates every sense of justice we have understood up to that point.
The pay-off for this is the abuse of freedom that we see around us.
Free agents sometimes choose to abuse their freedom, to do wrong.
If such a God existed, though, then he actually would prevent all suffering.
Suffering, though, is a familiar part of the world around us; it has not been prevented.
In making the world, God faced a choice: he could create free agents like us, or he could create automata, robots, without the ability to make choices of their own.
God chose to create free agents, and he made the right choice; a world containing free agents is clearly more valuable than a world of robots.