Can some lawyer explain the rationale of statute of limitations? Like why does a robber get to get away with the crime if they are able to evade the police for x number of years. Is it just because the trials suck after a while cuz no one remembers anything?

I recognize the value of the statute of limitations, but it is a technicality, and unfortunately, the central legal questions of this case were not addressed.

I am absolutely certain that if Sam was suing xAI and the case got dismissed on a technicality people would be lined up with screeds about the injustice of the situation.

It can be both

Then why did the American justice system needed nine jurors when a clerk could have sufficed?

The American judicial system is completely Byzantine and rotten, from top to bottom. Worse than many third world countries.