How do people learn languages just by watching shows??

I’ve met so many people who have become fluent in English just by watching YouTube or Netflix- I’ve met Moroccans, Malaysians, literally anyone I’ve met online from a non-English speaking country they’ve learned English by watching YouTube and I want to do the same with a different language (currently learning Spanish)

These people, do they just watch videos without subtitles or anything and one day it just clicks? I have asked my friends but they’re really vague about it lol.

If anyone has learned English (or another language) using this please can you tell me what you did???? How long did it take you to understand most of the stuff? With the Spanish shows I watch now I understand around 10% of it through my previous learning but if I can speed up that process I would love to know how