A lockdown isn't necessary if the population behaves as if there was, as the Swede's did.
People want to pretend they went on with life as normal but they didn't. They just didn't have the government make official what was already happening on the ground.
"As a whole, Swedes visited restaurants, retail shops and other recreation spots almost as little as residents of neighboring countries..."
Restaurants in the UK France Italy and Spain were totally shut for months. They had ZERO costumers.