1. There are very good CS guys around in Singapore, but most of them stayed back at school to do PHD. The reason is very simple: Singapore IT jobs have little coding skills needed and most of the time it is just project management (with most of the coding jobs outsourced) or support work (calling up vendors, standby when server down etc). There is no way for us to grow our talent once out of school. College is the last place where we can do technically challenging stuff, so those competent CS guys prefer to stay in school.
2. Our govt is infact the biggest employer of our IT graduates, doing the stuff of Point 1 above.
3. Despite all the woohoo that the startup scene in Singapore is trying to make itself into, it is really quite pathetic here. Cost is high, funding is little, market is not in this region too. Naivety is still the main driving force of startups in Singapore. Meaning those that want to startup in Singapore are probably really first-timers that do not know what they are getting into (especially fresh grads out of sch), and probably understood startup as anything that has the mixture of "tech+biz"
4. Companies do not value startup founders that failed, meaning if founders want to find re-employment in other companies, it is doubly hard for them cause employers do not understand what do startups do and how their experience in startups can contribute in anything. Startup founders that failed in Singapore is treated like a bankrupt equivalent.
So with job market that is generally not technically challenge, and startups that are technically challenge but not making it at all, it is simple to see why "talent" is not found in Singapore