The interesting thing is that like many people, they guessed that a lot of people would be contaminated during the 3-day weekend a week ago (great weather, cherry blossoms, and last carefree moments for people who will start their first job on April 1st). It's not innocent that Abe called for postponing the Olympics just before that weekend.
Koike could have asked the parks and popular venues (department stores) to be closed a week ago, but instead only asked people to refrain from going. What was poised to happen happened, and the number of infected people exploded half a week later.