Australia has an advantage because its one of the few countries where Football is not king. Several sports all have a fairly even footing.
For example, in England, all the best athletes want to play football because the pay is so much better.
But in Australia, a top class cricketer will make as much or more money than an AFL player, Rugby League/Union player or A-League footballer.
India is another example of a country where cricket is king but its fair to say that India seems to always underperform anyway.
In NZ, everyone wants to play Rugby, its the national sport.
In the west indies football is as popular as cricket. You can be like Dwight Yorke & co and earn millions, WI cricketers earn peanuts in comparison.
But cricket is also ingrained into Australia's psyche. There's a saying that the 2nd most important person in Aust after the Prime Minister is the Australian Cricket Captain. And its very true. Australia's captains are like Monarchs. They don't chop & change them. They say in charge for years and years at a time. It creates and maintains stability upon which the sport prospers. Every kid at some point wants to play cricket for Australia.
But quite simply, the talent spotting & development of Oz cricketers is 2nd to none. The best coaches, the best facilities, very high standard club and 1st class cricket comps, and on top of that, they don't get the talent pool excessively raided by footy codes like other countries.