Grimm tales

I read these tales as a young child and I have forgotten how disturbing some of them are and how harsh some of the lessons seem. Clearly the tales are to teach or explain (a lesson, a phenomenon, and so on) and sometimes have a quality of amusement (Hans in Luck for instance). What seems interesting to me is how Disney (among other children story tellers/movie makers) has swooped in and altered the tales for children. As time went on and I got further away from when I actually read the tales I thought of Grimm tales and Disney as much more similar than they really are. The first version of Rapunzel I saw on TV had no thorns to stab out the prince's eyes. Instead there was an epic fight between Prince and witch; the prince won and whisked Rapunzel away--completely cutting out years of desert wandering. I've been trying to figure out who decided to alter the stories for children instead of leaving them as more adult household tales and why.