Why did god create diseases?

[Esquilax]

Flawed beats indifferent
In the greater scheme of things, given overpopulation, for example, population control is a good thing. Promoting human longevity above all else is flawed.

Okay, I do have to object to this one, given that there's a much kinder way to deal with population control if you're god, and that's just to make humans less fertile.

The design you're positing is actually more cruel, where instead of just making it so we don't have so many kids to tax the environment, god instead creates death dealing microbes to cull the population at the top.