I saw an interesting explanation. Someone wrote "Judges are PR agents for the State."
A judge's job is to invent a clever excuse for taking away someone's freedom. Politically-motivated trials are "Verdict first, trial afterwards". A prosecutor decides that someone is a criminal. Then, he picks which law will be strictly applied.
For real crime (murder, theft, assault), you don't need a judge inventing clever excuses. Most trials involve "victimless" crime. For those trials, it's important for judges to be professional liars.
Consider this conversation:
Q: Why is X in jail?That would be obviously unfair.
A: The prosecutor didn't like him.
Q: Why is X in jail?Nobody is in prison for "criticizing the government". Prosecutors invent another excuse.
A: He criticized the government.
Consider the farce of "justice":
Q: Why is X in jail?Now, it seems fair.
A: There was a fair trial, an impartial judge, and an impartial jury.
Some lawyers wrote "The actual content of your legal arguments are irrelevant. The reputation of the lawyer matters a lot more than the legal arguments. Judges will bend over backwards, to rule in favor of insiders."
For a pro se defendant or plaintiff, it's even worse. The judge can rule against you. He has a monopoly. It's irrelevant if he's unfair. All he has to do is say "motion denied" or "I'm ruling against you." He doesn't have to provide an explanation.
Superficially, judges are supposed to be fair and impartial. In practice, judges act to protect insiders. A judge's job is to invent clever excuses for justifying State power. A judge's job is provide the illusion of legitimacy, when State thugs take away someone's freedom.