I think you mean why did "Australia, Bangladesh, Canada, Cambodia, China, Fiji, India, Indonesia, Ireland, Kiribati, Korea, Hong Kong, Maldives, Mongolia, Myanmar, New Caledonia, New Zealand, Philippines, Samoa, Singapore, Sri Lanka, Sweden, Thailand, Tonga, Tuvalu, Vietnam, and UAE" implement ADS-B before everyone else?
This is misleading.
Australia is the only country in the world implementing ADSB for ALL IFR aircraft in ALL airspace types at ALL altitudes.
Other countries have exempts below a specific altitude, in class G airspace and or for private IFR flights.
Pretty much 12 months on after we spent $40k to fit ADSB to be compliant with the original deadline, what benefit have we seen? PRECISELY NONE. We still get messeed around in CTA frequently routed around the light aircraft lane but just above it to be in CTA. We are not seeing any benefit from reduced separation (in fact I'm told that has never eventuated) and we are not getting any benefit from traffic advisories because in class G about 99% of traffic is non ADSB equipped VFR traffic (even in IMC).
ADSB has been another debacle, along with ELT's and Part 61.