With some oversea working/races experience in different region, i think it is much more toward a climate thingy, local population density and life style habit.
Under a cooler climate, ppl will tend go out for outdoor activities. I agreed with you that based on our local climate unless ppl have strong interest or else most other will prefer to stay indoor with AC. When i in temperate country like england, seasonal weather enable ppl to just sit down at the park even at noon. (who will do this here?? ) Other than temperature, the high humid con'd also make sweating feel worse. Expect a crowd of supporters to attend a outdoor event etc under a hot sun... slim chance. (Q' for iphone/lottery consider under strong interest category...)
Other region where a big race event actually able to boost economic and liven within that town. Thus local population will tend to be more supportive (even maybe 5% of the local pop attended as supporters, it can become a huge crowd) as it is out of norm in their town . Buz owner will try to make their buz relevant to the race/event in order to attract more customers. Sg is too small to even consider the race venue as a separate town and gain the above conditions.
Lastly life style, physical activities such as running, yoga etc is growing its popularity. But our national favorite pass time is still eating. Ppl spent a big amt of time/effort and money to travel/queue for food. Other than feasting, activities (regardless physical or cultural ) won't able to spark up to the majority.
With or without local authority support, my opinion is that it won't able to spurt much from public regarding to these.