The "trauma" from staying at home? Please. If the parents let them watch youtube for 2 years then the parents were stupid. I have 3 kids in school, all but one of them were in school at the time. Staying at home with Grandma and Papa while they did zoom school didn't break their brains. You know what my kids don't have? My kids don't have a smart phone. You know what my kids don't have? Unlimited access to devices.
Now, I will say that the Pandemic was pretty traumatic here in the US, at least a million people died last time I looked at it. Those people were somebody's neighbors, grandparents, uncles, etc. So maybe the realization that "nobody gives a shit about you except for your productivity" was a lesson they internalized?
Largely, I think it is the parents though. Like I said, I have kids, and when their grades slump, I get on them to fix it. A lot of people are really unwilling to do that.
> I have 3 kids
So they got at least some of what a lot of kids missed out on: socialization.
With homeschooling, parents go out of their way to find other kids for theirs to socialize with, but during lockdowns this wasn't allowed (if the parents even had any idea about it, since it was forced on them and not something they chose to do).