I don't know the "real life events" on which the story was based, but I would guess in real life:
Anyone in almost any legal procedure MUST be represented either by their own council OR an ad litim council or by themselves. If by themselves, it must be a freely chosen course of action by the person being evaluated in a proceeding.
Since in the proceeding I witnessed, my MIL did not oppose the guardianship, and she chose to represent herself and she WAS heard on the matter in court. Had she simply said "I contest this action" that would have halted everything and begun essentially a court hearing in which evidence would have been presented. Because she did not contest, the matter was quickly settled. Otherwise, her various doctors would have been sworn and would have testified. She would have been able to present testimony of other witnesses to her competence.
Collusion is not unheard of in the justice system, but it's relatively rare as it takes a lot of people to collude - even in a simple procedure. It would require at least one colluding judge, one colluding plaintiff, one colluding plaintiff's attorney, one colluding witness (like a doctor) and one colluding attorney for the person being evaluated.
I too would be concerned about someone seeking guardianship over me, but I don't think it's as easy as picking an old guy like me and going behind my back with some paperw*rk. I WOULD be contacted and made aware. I WOULD have opportunity to retain council. I WOULD be allowed to have my own witnesses (like a different doctor(s).) I WOULD be heard in court. Anyone with enough resources to be a target also has enough resources to fight guardianship. YMMV