this is completely anecdotal and you're making a ton of assumptions. firstly, that parents are always better suited to raise a child then anyone else, like grandparents. this is unequivocally untrue. some people have extremely fucked up parents and are better off being raised by anyone else.
secondly, just because you don't know any examples of someone being raised by their grandparents who isn't a fuck up doesn't mean that is the case always, but i know you know that.
the issue here has nothing to do with this kid living with his grandparents.