Why are Covid cases going down?

Imagine if the government had taken notice of the assorted scientists who, a couple of weeks ago, were imploring them to immediately enact ‘Plan B’ and reintroduce measures such as compulsory mask-wearing, working from home and limits on gatherings. The current dip in new Covid cases would be heralded as a sign of the success of the policy, and there would be calls for new lockdowns, or semi-lockdowns to control Covid infection numbers in the winter.