A few months ago Singapore had a model example for dealing with Covid-19, but it recently had a mass outbreak.

So what went wrong?

Well to understand this, it would first help to look at what it did right. It cracked down immediately on travel - specifically outside contact. it being an island helped out quite a lot.  

The biggest issue was the overlooked migrant workers and an underestimation of how infectious the disease was. The place where the migrant workers were being kept were dormitories as well, which meant they were being kept at close quarters with one another. Unfortunately that mean now that Singapore is caught between a rock and a hard place, meaning that they have to start implementing new policies - with harsh punishments in order to put a clamp on the new wave before it catches too far off the ground.

https://www.cnn.com/2020/04/18/asia/singapore-coronavirus-response-intl-hnk/index.html