and once those black markets are in place you have a rather thorny problem. growing drugs is not mainly an agricultural skill, it is primarily a networkiig skill. a grower or dealer won't go straight because you've made the thing they do legal. they'll pivot to something else you've made illegal. but the best way to erode the black market isn't to target the cartel, it's to target the street level dork engaging in dangerous behavior because they're desperate.

the less desperation there is in the ecosystem, the less criminal behavior there will be

Not the point I know but:

Australia....had forced buyback in the 90s after the port shooting....60% turn in rate, 1mil owned arms by civs...today 3+Mil firearms owned by citizens in Australia...so did it really work? Or did society get less violent because of the education and safety nets that Australia has?

No the buyback wasn't actually that effective as you noted, crime was already declining before the ban and as you noted number of guns increased since. Similarly in the US gun ownership (both % of gun owners and # of guns) have increased and violent crime of all kinds have decreased in the US in the same time. I "blame" surveillance states and probably stuff like taking the lead out of gas, personally. Also the same style buyback in the US would be monumentally expensive, not effective because of resistance, and not effective because of lack of social safety nets (listed separately on purpose.)