How does the court go about choosing an appointed guardian? ?

According to our attorney, if the family of an elderly person (institutionalized with dementia) thinks someone is abusing power of attorney for personal gain, they can file a motion to have the court appoint someone legal guardian, and that person's authority super cedes the power of attorney. If the family doesn't specify a particular person to be the legal guardian, how does the court choose someone, especially if it would be better if the guardian came from outside the family, but the family has no idea who it should be?