No, Matt Amodio did not win 38 straight matches on Jeopardy! because the producers were deliberately feeding him really easy questions. And, no, he did not finally lose last night because they got tired of him and rigged the game so he would (or, in an even more unlikely scenario, that he agreed to throw last night's game).
I watched every single one of Amodio's appearances and here's what I saw: He is very fast on the buzzer, so fast that it often seemed that he was ringing in before he was sure he knew the correct response. Go back and notice how many times he has to wait a bit--clearly thinking his answer through--after being called on. When a Jeopardy! contestant knows the correct answer, he or she is eager to give it, in my experience, often not even waiting for the host to finish acknowledging them before speaking. They only pause when they are still trying to come up with a response.
That speed allowed Amodio to control the board and hence, usually, pick the clues he wanted to see--avoiding categories in which he wasn't as confident--and find the Daily Doubles far more often than his opponents did. But last night, confronted by two opponents more nearly on his level of knowledge and reflexes, he lost that edge. He never got even one of the Daily Doubles, and his challengers correctly answered all of them.
In addition, I think Amodio got desperate. He began ringing in even more often when he wasn't sure of the answer, and got far more responses wrong than usual....and that resulted in a double penalty: He lost the value of that clue and his challengers had the opportunity to give the correct answer and thus win that same amount. (It can also be said, by giving an incorrect answer, Amodio made their job easier by thus eliminating one of the possible responses.)
And now, the reason why the producers would not "rig" the game: it's illegal. After the quiz show scandals of the 1950s, Congress amended the Communications Act, in part, to make it illegal
To engage in any artifice or scheme for the purpose of prearranging or
predetermining in whole or in part the outcome of a purportedly bona
fide contest of intellectual knowledge, intellectual skill, or chance.
And the penalty?
Whoever violates subsection (a) shall be fined not more than $10,000 or imprisoned not more than one year, or both.
https://www.law.cornell.edu/uscode/text/47/509
Not to mention undoubtedly losing their job, never to work in the entertainment industry again.
All it would take for such a scheme to come to light is for one contestant, one production assistant, one stage hand, aware of the conspiracy, to step forward and blow the whistle. Would you risk everything on the chance that no one of the scores of people involved in a production like Jeopardy! would spill the beans? Look how quickly Mike Richards lost his job for something that was in no way against the law.
I know "conspiracy theory" is the new on-line meme, but this one makes even less sense than all the ones about our last presidential election.