Everything does happen for a reason, but not in the way that's usually meant by this. Everything that happens is caused by something else. For example, the reason I am writing this comment is because of what you wrote. And the reason you wrote what you wrote is because you wanted to. And the reason you wanted to is because...and so on...

But what people usually mean by "Everything happens for a reason" is that there's some grand beautiful plan that all makes sense. That's nonsense.