Aust has always been lax on tariffs. Aussie gov'ts Labor and Liberal have alway relied on quotas, ADRs and brand selectivity as I recall in the 70s.
When I bought a new Datsun 1600 off the showroom floor and then went on overseas pharmacy trips, I noticed that many countries had tariffs of 100% on imported cars.
A Yu Loong (aka Datsun) would cost little in HK and Taiwan, but a Holden would cost 2.5x as much as here.
Aust was afraid of losing sales on agriculture as a trade off, and even since then, Aust is still only imposing luxury taxes whilst Holden wilts on the vine.
Combine that with the fact that over the past 20 yrs, the Aust gov't has forked out over 2.1 billion propping up GMH whilst unions have successfully gained higher and higher wages (and bonuses) for the blue collar guys. The golden egg is now dead for these guys.
In short, everyone is at fault. If I was given the choice of buying 10x GTSs (to keep Holden breathing) against 10x grey imports of my choice, I'd still choose the latter. So consider me at fault too!!!