I've read a theory that the reason Singapore has so many is because of air conditioning being used so much.
They are using aggressive contact tracing as part of that, so if it were spreading like wildfire through A/C vents surely that wouldn't be effective and they would have a much faster growth rate of cases.
I'm in Singapore, and life here goes on pretty much as it always has. Except for a larger than normal number of people wearing masks, you can't really tell that this is ongoing.
That said, the government is doing a lot to keep it that way. There is intensive contact tracing, and companies register people going in and out of their offices (to help tracing), if you're sick you're supposed to stay at home, and so on.