Also Oil and Gas is core industry for Singapore economy. So when anyone fills gas it helps government revenues and generate jobs. Climate is not the primary concern given the small footprint of Singapore.
Also if Tesla comes in Singapore as it is perfect place for its range BMW, Benz which are the primary brands will suffer heavily. Also thousands of jobs repairing gasoline engine, oils, filters will be lost. Since electrical car do not have as many mechanical moving parts as traditional gasoline car it will reduce maintenance costs and car servicing and parts related business.
So Singapore won't let Tesla setup up easily. It will be taxed higher than other electrical car companies which works on fringes and do not threaten the oil and gas related automobile jobs and taxes.