We are talking about the benchmark game here. The code for different languages was written by different programmers. For some languages, there were multiple implementations and many iterations. In this case, the researchers used the fastest one.

Some of the implementations are extremely optimized and took a lot of effort. Some implementations are not. So you might be comparing highly optimized JavaScript code with naive, below-average TypeScript code. You cannot compare those.

It would be much better if they used the same level of optimization for each language, but they didn't. Furthermore it is called a "Game" (it used to be called a "Shoot-out") because you shouldn't take it seriously. So it shouldn't be the basis of serious research.