So far as public versus private is concerned, a bit of a history lesson and noting that we seem to be repeating how it all started.
To cut a long story short, Victoria and SA both started out with privately owned electricity industries with production based on the use of black coal. Tasmania started out mostly privately owned, using a mix of resources (sub-bituminous coal, oil from shale, hydro).
By 1916 Tasmania's power industry was primarily in public ownership and the state's first major energy-intensitve industry had commenced operation. At this point Tasmania was the only state with a transmission system in operation, indeed at that point Tasmania's was among the longest in the world.
In 1917 another major energy-intensive industry started up in Tasmania. Meanwhile Vic and SA were both grappling with ongoing fuel and power shortages.
1919 - Tasmania now has a grid as such running from north to south with two power stations connected and works underway to rapidly expand the system. Meanwhile Tas was aggressively marketing it's electricity supply to industry located elsewhere, primarily Victoria, in an attempt to encourage relocation to the island state.
Victoria sets up the SECV to resolve the state's power situation with a direction that local resources shall be applied to the problem.
A key point here is that private enterprise has failed to resolve the problem of Victoria's unreliable supplies of coal and in turn gas and especially electricity. With Tasmania now actively trying to poach Victorian industry, the Victorian government had little choice other than to resolve the problem.
In 1924 the SECV had their first brown coal mine (Yallourn) up and running along with a briquette works (producing a substitute for black coal) and power station (Yallourn A) using raw coal straight from the mine also running nearby. In 1928 the SECV had added hydro to the system and in due course an assortment of new brown coal power stations, briquette works and hydro schemes followed.
Victoria also set up the Gas & Fuel Corporation for the same underlying reasons, they needed something that wasn't dependent on unreliable supplies of black coal. In 1954 G&FC had a gas works using brown coal up and running, plus the first gas transmission pipeline in Australia, and was supplying about a third of Melbourne's gas from that source.
SA faced a very similar problem, that of privately owned electricity and gas companies being unable or unwilling to shift to alternative fuel sources (SA also having ongoing shortages of black coal). The SA government had tried for a very long time (decades) to convince the Adelaide Electric Supply Co to use the state's local coal but they point blank refused.
In due course, and faced with the reality that both Victoria and Tasmania were now far more attractive to industry with their cheap and increasingly abundant power supplies, SA acquired AESCo by force (actively resisted by AESCo) and set up the Electricity Trust of SA (ETSA) to replicate what Victoria had done with the SECV.
ETSA quickly went about coal production, mixing it with black coal (which at that point was coming from wherever they could get it including imports from overseas) in former AESCo power stations not designed to cope with the local lower quality coal. In 1954 ETSA opened its first purpose built power station using Leigh Creek coal and in 1960 a second, much larger, station was operating. SA had now joined Tas and Vic in having cheap, abundant power with the associated economic benefits.
So historically at least is was certainly the case that private enterprise failed at the task of ensuring a reliable electricity supply and failed even more at the task of changing from established technology to something new. It was simply easier, less risky and not unprofitable to stick with what they'd always done rather than risk a fortune on something that may or may not work (and there were plenty of technical challenges in Vic and Tas).
Other states were slower but in NSW they ultimately had no real choice. Victoria had the massive Hazelwood power station, several times larger than anything in NSW at that time and an order or magnitude cheaper to operate, under construction while Tasmania was building one hydro scheme after another with multiple new schemes under construction at once. And then BHP dropped the bombshell - they'd done the deal and were relocating their entire ferro alloy, a key part of steel production, operations from NSW to Tasmania with power being the reason. All of a sudden NSW was pretty keen on electricity lest other industries also packed up and moved to Vic, Tas or SA.
All that said, public ownership wasn't perfect by any means. It's no secret that unions had a rather strong influence within the SECV, at times crippling power production through their actions (a situation which rather suited Tasmania by the way - not once have the lights gone out in Tas due to a strike and that was always a good marketing point to industry albeit one done discreetly).
Then there were the technical dramas. The SECV put a lot of effort into getting the Morwell mine and briquette works built only to find that the coal was unsuitable in just about any boiler. It seems that nobody thought to test it, simply assuming it to be the same as that found at Yallourn just down the road. For the next half century coal from Yallourn was transported to Morwell, a ridiculously uneconomic operation given the coal is almost 70% water, as raw material for briquette production to work around that problem. Morwell coal was ultimately put to use in Hazelwood power station, being burned at low temperatures (they called it "cold combustion") to get around the fouling problem although that was never perfect and still isn't today.
But despite a few blunders public ownership did achieve the goal of getting a cheap, mostly reliable power supply in Victoria and other states.
Now Vic and SA are both privatised, those states having pursued privatisation earlier and more aggressively than anyone else in Australia. Those two states are now the ones facing the biggest problems with regard to ongoing power supply and that's not a coincidence. It's even funnier when you realise that of the new supply capacity added in Vic since privatisation, the majority is either from Tasmania (which is still publicly owned), or has been brought about by Snowy Hydro (also publicly owned). Hmm...
I'm not ideologically opposed to privately owned electricity though. It could work if set up and regulated properly to achieve the required technical and other (eg emissions) outcomes. Where it fails is if it's left to pure market forces on a commodity basis and there's a simple reason for that - electricity being very different to any other commodity since it can't be stored. Just because the price of the commodity is low right now doesn't mean there won't be a desperate shortage tomorrow and then an oversupply a few hours later. That's massively different to other commodity markets and is why market forces alone won't produce a reliable supply using that model.
Under a different model, one focused engineering rather than financial speculation in a ridiculously volatile market, private ownership ought not be a problem as such. That's a long way from where we are today however with even the remaining publicly owned operators playing the financial game whether they like it or not (they literally have no choice since that's the law).