That's your limited opinion talking. You can't conceive of a being greater than yourself so you place your own limits on Him so you can claim He doesn't exist because He doesn't fit into your limited understanding.
It's your opinion that there was no purpose. Here's one potential purpose, the nation of Israel was established as foretold by prophesy. Without the Holocaust, it would not have happened.
That's your human "logic" speaking.
Consider, a one-year-old gets angry when Daddy leaves every morning and won't play with him. He has no concept that Daddy has work to do. He has no concept that Daddy will come back home every evening and play with him. He just gets mad when Daddy leaves. That's where you are. You simply can't comprehend beings higher than yourself, so you claim they don't exist. The reality is, any being great enough to have created you is self-evidently more complex than you can imagine.