Schools might never have closed in the first place had the coronavirus not started in China. Imagine it had started in Sweden. Whoever responded first was going to set the tone for the nations that followed. When we are uncertain about what to do, we look to the behaviour of others to guide us.
Imagine walking down a street with a new restaurant on either side (you remember restaurants, right?), and that you do not know anything about either of them. One has some customers inside, the other has none. Assuming you can get a table, you would choose the one with people in it because, in the absence of any prior knowledge about the restaurants, other people provide you with a signal about which to eat in.
But imagine that the first person walking down the street had no idea which one to choose and did so based on a spurious reason, such as preferring a red door to a yellow one. The restaurant with the red door would get all the customers while the one with the yellow door would get none, and this would provide no information at all about which restaurant is better.
Now consider China’s response to Covid-19, which was to lock down Wuhan. It chose the red door of virus suppression and school closures over the yellow door of mitigation and leaving schools open, with the eventual result of herd immunity. It might have done this for spurious reasons so far as mitigating impacts are concerned, for example because it felt bad about being responsible for the virus. But just as people follow others into a restaurant, most countries followed China’s lead.
Now there were of course epidemiologists who advised suppression because it was expected to result in fewer deaths from Covid-19, and so it has a more rational and substantive basis to it than choosing a restaurant simply because of a preference for a red door over a yellow one.