Many of the Grimm tales in their original form were also somewhat bizarre or surreal. I agree with you, but sometimes think the Disney versions were crafted as they were in part just to make sense as much as anything.
There’s a theory that Hansel and Grettel represents a cultural memory of a time of famine where children were abandoned, left to starve.
I think they all used to live in a very different reality, with people dying at an earlier age and much more often then they do now. Also infant mortality was much much higher in the olden days; it was a scary time, altogether.
The olden days didn't have the luxury of clean water, antibiotics and food plenty. These are quite recent inventions...