I lived in East Asia, as well as Singapore, for a few years. Here are the main reasons I think:
1. Very restrictive gun control; outside of some hunting enthusiasts, almost no one has a gun.
2. Social cohesion, meaning people are less likely to deviate from the behavior of the crowd (murder would be a significant deviation). There are downsides to this as well, as people go along with certain normalized behaviors (imperial Japan, tolerance for certain types of corruption/cheating that we find reprehensible).
3. Homogeneity may play a part, but Singapore is incredibly diverse (racially, linguistically, religiously, economically) and is one of the safest places in the world.
4. Economic prosperity; here I’m thinking about Singapore, Korea, Japan, Taiwan primarily. But in general these countries are fairly well off, and there’s definitively a relationship between wealth and violent crime. Crime is much higher in nearby countries with higher poverty levels (Mongolia, Vietnam, Thailand, etc.).
5. Social mores. People in Singapore are, for the most part, very well behaved and respectful of the law. Same in Japan, and to an extent Korea. People will rarely jaywalk even if there is no traffic in Korea (I once got stopped and questioned by two police officers when I did it). I think a difference in Korea is that under the cloak of anonymity, they tend to be more boorish (some very rude and aggressive drivers there, unlike Singapore and Japan).