As far as i know, Bowling was put in as an Exhibition sport by the Malaysian Comm Games Ass. Like the olympics, there are mandatory sports and then the Host organisation can select other sports to put in the program.
This is done by an application to the IOC/CGO after the host city has won the Bid. Malaysia put it in as it is a strong sport for their country (HA HA HA but we swept the medals)
this is what i understand happens, and apparently Melbourne chose Mountain biking or something obsure like that