People discuss policies all the time, and take inspiration from jurisdictions where those policies /appear/ to be implemented and "working"

The idea that there is an age requirement (for certain content) has been around for a very long time (Facebook, for example has a no under 13s rule in their T&Cs, many porn sites have a 18 years or older declaration before allowing access, and so on)

Australia has recently implemented law(s) that take the next step forward, and the other countries in the world that have been wanting something similar are seeing that, seeing that there haven't blowback from corporations or voters that makes the idea of the law unpalatable, and thinking that they too can implement laws that work in similar ways.

If you actually pay attention to global politics you will see that this sort of behaviour occurs fairly regularly (look, for example, and the legalisationg of homosexual marriage, there was a law legalising it in the Netherlands in 2001, then Belgium did similar in 2003... and so on as more countries saw that their own voters were amenable to the idea https://en.wikipedia.org/wiki/Legal_status_of_same-sex_marri...)

edit: There's no grand conspiracy at play

Another example is the cannabis use laws, cannabis was heavily criminalised in the 70s, there was pressure from the USA for other countries to follow suit.

BUT from the early 2010s several states of the USA legalised recreational use - this has also bought the debate back to the fore for many countries, with reassessments and changes occuring https://en.wikipedia.org/wiki/Legality_of_cannabis_by_U.S._j...