Bad writing. Homer's parents...

It made no sense. So Homer got a little dumber because of accident. They visited him and then decided he will not get better and just stopped. But the thing is - they had no other children.

Like fine if it would be like in Rain Man when parents got Tom Cruise and put Dustin Hoffman in facility because he was dangerous to little brother. But Homer's parents had no one. No one to leave their estate to. Were they not bored?

And Homer was not as stupid as movie tried to pretend he was. He was normal. If they would not keep reminding that he is brain damage - I would have never notice. He just seemed like eccentric guy. He behaved like a normal person.

Writers really should have write in sister or brother. To make that "parents abandoned him" believable.