The Japanese government acted to isolate the cruise ship and were in the end trying to protect the mainland Japanese citizenry, and the fact that the quarantine conditions were not of a high standard is not a direct result of government involvement. In defence of the Japanese government, this was not a clear situation in the very start of the COVID-19 outbreak, before it had even been declared a pandemic. Many of the people allowed to leave the ship were testing negative aboard the ship, but later displayed symptoms, indicating it is more difficult to accurately deal with the virus than most people are willing it acknowledge.
When Professor Kentaro Iwata publicly condemned the conditions on the ship the criticism went viral, but the professor quickly retracted his criticism citing he was “informed that significant improvement was done inside the cruise ship"  shortly after his inspection. Many unforeseen issues have cropped up during this crisis and continue to, even at this late stage in the pandemic, new symptoms, fatalities, and vulnerable demographics are beginning to present themselves, such as a new inflammatory disease in children in New York, could to be linked to the SARS-CoV-2 virus. While it is easy to accuse the Japanese government of failure here, some reflection on the bigger picture of the pandemic is probably useful to put the situation into a more realistic perspective.