I haven't really followed it closely but it seems like a waste of money and unlikely to help Japan's economy. I mean all recent Olympic games have been wasteful but in this case they don't even have the benefit of tourism to offset the cost.
I'm not sure if the games will have much of an impact on COVID-19 spread. With no fans and with aggressive testing/quarantines for athletes they might be able to get away with it.
Even with all these things, the authorities had to conduct the tornament. They can't delay it further because in 3 years time 2024, we have the next Olympics.
Japan may not have collected money from tourism or crowds but there is a lot of sponsorship these days. We cannot say that Japan did not earn any money by conducting the Olympics.
When we can have Euro 2020 and other sports in these times then why not Olympics ?