I'm too young to remember before 1996, but my dad was and was a gun owner, and I'm a former Australian gun owner (and current New Zealand gun owner)
Guns were not outlawed in 1996, licensing requirements and restrictions on the types of guns allowed became more strict. The differed a lot from state to state but pre-1996 laws were basically:
License required to buy guns in most states (but this often went unenforced)
Pistols heavily restricted and needed a separate stricter license
After mass shooting in 1996:
Non-semi-auto rifles and shotguns restricted, registration required
Semi-automatic rifles and shotguns heavily restricted, and a good reason to own one is required
Laws for pistols mostly unchanged
Then, after another mass shooting in 2002:
Yes there were protests, but as far as I know they were never larger than a few hundred people
My dad was a gun collector who kept his guns in a strongroom so he didn't need to do much, he already met the requirements so he could just pick up the new license, but a lot of his guns simply weren't allowed to be owned anymore, with no available license or anything he could do to keep them, so he had to sell them off, because the only alternative was having pieces of history pretty much destroyed by deactivation.
Overall, I think it was right to further restrict gun laws, but the laws that were put in place are heavily flawed and nonsensical, for example plastic-pellet shooting airsoft toy guns being in the same category (cat R) as rocket launchers, and semi-automatic revolving rifles like the Rossi Circuit Judge being in the same category (cat A) as air rifles. And the tone of the government seems to be complete disregard for shooters and being outright hostile to them, whenever a new of fun thing is on the horizon for Australian shooters (H&K R8 rifle, Adler shotgun), the government makes sure to jump in and shut it down simply out of spite.
Overall, I would not recommend Australia's gun laws as a model for other countries to base off, as a current New Zealand gun owner I think their laws are far, far better. NZ's strike a good balance between restricting guns and vetting their owners, and not stomping over gun owners with pointlessly restrictions that do nothing to prevent crime.
New Zealand may allow silenced semi-automatic rifles on a basic license and collectors to own artillery-pieces and machine guns, but gun crime is almost non-existent, because instead of simply banning things for everyone, they instead focus on vetting owners, so that the right people who are qualified to own them still can.