How does RXJS manage for subscriptions to trigger sending data only to that subscriber?

[PhilippMDoerner]

This question is mostly aimed at the implementation of RXJS because I'm trying to write something similar in another (nieche) language with a very rigid static type system and I'm struggling at this aspect.

When you have a cold observable and you subscribe to it or any observable derived from it, you only trigger sending data to that one observable. Example:

import { of, map } from 'rxjs';

let obs = of(1)
obs.subscribe(x => console.log("First value subscribe", x))
const mappedObs = obs.pipe(map(x => {
  console.log("Compute happens")
  return x*2
})); 
mappedObs.subscribe(x => console.log("Does not get triggered by another subscription", x))
mappedObs.subscribe(x => console.log("Does not trigger the other subscription", x))

However, since observables are lazily evaluated, mappedObs here never holds any value. It's just an operation stacked on top of obs which starts pushing its value through the entire pipeline upon a subscription.

But that subscription triggers only sending the data to that specific subscription, not to all subscriptions (which makes sense).
That means somehow you're figuring out through the DAG of Observable-objects and other intermediate observable objects that maybe get created (?) where the source observable is and are pushing values through the pipeline from the source-value to the subscription and nowhere else.

I honestly am struggling to understand how this is all architected by reading the source-code, so I'm trying to see if somebody maybe can give me the high-level idea on how the implementation technically works in hopes of maybe being able to learn from that.

I'd also happily take links to any kind of resource that doesn't just try to do very basic reimplementations of the observable pattern in JS, which is almost everything I find when I try to google search myself.