I was on a TV game show in 1970, at the tender age of 20 (The Who, What, or Where Game). Jeopardy was still on in the daytime, back then, hosted by Art Fleming. I tested for both shows on the same day.
Anyway, there is no question whatsoever that the producers and the stage manager (who is a different person than the host) pick the guests and pick the categories to heavily influence the outcome.
In my first game, I was on against a woman, a welfare mom who came to NY on a bus ticket and won four in a row. If she won #5, she was going to get some big deal prize. She was, IOW, supposed to win.
But I won. The stage manager/assistant producer was not happy.
The next game, I was on against an old man FROM MY HOME TOWN (how often are 2/3 contestants from the same little place).
Every category was for him - Big Bands - The Roaring Twenties - Old Cars - World War One, etc, etc. We were tied at the end, he got a tiebreaker - "What is the name of the COUNTRY in the South of France with the famous casino?" His answer: "Monte Carlo". They gave it to him, and I was out the door.
I'm sure there's much. much more to Jeopardy, but based on your test scores they have a pretty good idea about how to stack the board if they want you to win, and if they want you to lose.
Obviously a guy like Holzhauer has very few weaknesses, and also obviously he was good for business.
But if they wanted him gone, I'm sure between picking the right opponent and whatever they do with the buzzers, even he would be gone.
TV sucks.
I have no idea how the inner workings go but I have suspected the exact things you say. I also know they claim that it is impossible to do what they are doing.
The contestants probably have no idea.
You KNEW it was Curtains when Alex showed a Get Well Card from James' daughter!