COVID had some some circunstances that helped becoming so widespread. It takes several days for someone to caught it to develop symptoms, if ever. It happened

COVID had some some circunstances that helped becoming so widespread. It takes several days for someone to caught it to develop symptoms, if ever. It happened at a moment in time and place with very high connectivity with the rest of the world You have far less odds of having severe symptoms (specially in the main/original variants), if any, if you are young enough. That is a good age for international travel (and spreading) and to not not care about consequences for others. And, last but not least, the influence of social networks and agents on them, that denied that the disease was a risk, that people should not take measures, and now that you should not vaccinate. And conspiracy theories, of course.