But now that I thought about it, I realized that the beginner’s luck had more to do with the player itself than outside factors. As a beginner, you have no expectations. You do not know what’s possible. What can you win, what can you lose. There is no pressure of playing which is why you are just able to win. But a few rounds after that, you are already expecting to win. There is the need to perform better and get more money than the previous round. And that is the explanation for a beginner’s luck. It’s just our mindset.
Beginners luck doesn't necessarily have a whole lot to do with "you have no expectations. You do not know what’s possible. What can you win, what can you lose. There is no pressure of playing which is why you are just able to win. But a few rounds after that, you are already expecting to win", it's really just saying that someone came up with some 100+ years ago or whatever and it stuck.
It's just unlikely newbies will be good or "win", so hence the nickname.