Not to deter any further discussion, but u/CrossyNZ tackled this question previously here.

The answer written by u/CrossyNZ, linked to by u/silverappleyard, is written from a New Zealander perspective and is also a fairly good TLDR of what I've written, so maybe read this only if you REALLY care about an Australian perspective. This is a topic easily large enough for a book, so I apologise that it's the longest thing ever written on the internet - I seriously tried to chop it down. The format is essentially a summary of Aboriginal-settler relations, followed by comparisons with Maori.

The reason Maori and Indigenous Australians were and are treated differently is the idea of civilisation, and what that means to a European Christian settler, even in a seemingly liberal, progressive and secular society. From first contact to today, explorers, settlers and native-born non-indigenous Australians have deeply misunderstood the nature of Aboriginal life before and after colonialism, and the findings of academia have often been thrown out in favour of a national-cultural narrative of racial and cultural superiority, often in line with views common in the US and the UK of the time.

Explorer Attitudes

In their first (secret) reports to their VOC masters in Batavia (modern Jakarta, Indonesia), Dutch captains who explored the coasts of northern and western Australia in the 17th century reported that both the people and continent itself were ugly, poor and wild. Based off of old geographer theories on a terra australis incognita (unknown southern land), first theorised by the ancient Greeks and rumouring the existence of great mineral wealth and lost civilisations, the VOC financed expeditions to this unknown land to see what wealth or trade goods they could claim in the name of the company. These expeditions usually started as attempts at finding lost ships and sailors to recover their cargoes, downed by treacherous reefs – the Dutch captains often found nothing in their searches but death at the hands of seemingly wretched black savages who could not be reasoned with, resulting in a massive waste of funds and a deeply negative review by the VOC.

Around the same time (1688 and 1697), English pirate William Dampier explored the north-west coast and wrote journals about his finds, sharing with Britain great deals of strange flora and fauna, but also lurid tales of ugly savages who ran around naked and starved in a desert land. Dampier was a smart man – not only was the first explorer to act scientifically in Australia, he also knew that if he wanted to sell books back in London, he would have to tell people what they wanted to hear, and they wanted ugly degraded savages. He reported that Aboriginal Australians were ugly and totally lacking in sophistication, often unable to feed themselves and jealously guarding what little food they could find, “the most miserable people on Earth”. His books were enormously popular, and especially inspired the later generation of English explorers, like James Cook and Joseph Banks (and much later, Charles Darwin).

Cook, exploring the eastern coast in the 1770s, seems to have had a more favourable view of New Holland, complimenting both the land (the eastern coast being greener due to having mountains and more rivers), the people (occasionally calling them ‘beautiful’), and the flora and fauna. Cook saw a happy and healthy people, claiming them to be the happiest on earth, and living in total bliss despite a lack of possessions and agriculture. He and Banks also wrongly believed that the land must be empty beyond the immediate coast, and that the Aboriginals were totally nomadic and thus would happily move along should the British settle. He may have had an agenda in all of this though – he, the scientist Banks, and the crew all had a mind to settle this land, and thus may have intentionally painted a prettier picture so as to win sponsorship of an expedition, scoring land grants in the process.

With the American Revolution in 1776 came an end to convict transportation to the American colonies. This need to get rid of excess petty criminals, plus interest in supplying flax and timber, a far east naval base, scientific exploration and beating the French (who also explored Australia extensively in this period), led to the creation of the First Fleet which founded Sydney in 1788.

Settlers and Settlement

Over the next one hundred years of British settlement across the continent of Australia, the exact same circumstances played out again and again as they had on 26th of January in Sydney. A small group of white settlers lived in fear of a small tribe of Aboriginals nearby, totally ignorant of each other’s cultures, and mostly unwilling to learn or change their ways. Official British policy was always to respect the lives and traditions of the locals, to make treaties where possible and try to win them over to becoming British subjects. The British garrison (small, poorly trained and supplied, and mostly for show) was almost never used against Aboriginals, unless pushed to do so by a fearful populace. The idea of the nomadic Aboriginal was quickly proven wrong – all Aboriginal tribes defended their lands to some degree, all treating Europeans as hostile invaders, and thus attempting to deal with them in tribally appropriate ways. In some cultures, guests were to be ignored for a few days – thus, some Dutch and British explorers noted that some Aboriginal tribes were totally unimpressed by ships, clothing and firearms, to the point of obstinately looking away. Some tribes believed in gift-giving by guests, so were not surprised when explorers offered them beads and textiles in welcome – however, not valuing these items, they became offended and attacked, and thus the Europeans shot them, not understanding how things had turned and putting it down to ‘stupid savagery’.

Aboriginals also had different means of warfare. Many tribes practiced ritualised warfare, something akin to a duel or a public maiming – often when a white settler shot an Aboriginal for stealing food from their farmland, the tribe would return and stealthily kill someone else. This was unprovoked murder in the eyes of Europeans, but for the tribe, it was tribal justice – a man from their tribe was killed, so a man from the white tribe was also killed, restoring balance and quelling any need for revenge. Explorers also noted genocidal tendencies between different tribes – deadly night raids where men from one tribe would silently butcher all of the other. Obviously, witnessing such events deeply frightened the isolated Europeans, leading to a heightened sense of panic and revulsion. This panic became mixed with Aboriginal knowledge of the land, how to live in harsh environments, and stealthy fulfilment of secret motives led settlers itching to form parties to go kill a tribe nearby before it struck them in their sleep – which was easy to do, on their isolated farmsteads. It was near impossible for authorities to dissuade these groups, and they usually had no incentive to do so. Posses of settlers would ride out, hunt down a group of Aboriginals, shoot all they could find, ride home and tell everyone that they’d won a battle – often 20-30 Aboriginals killed, including women and children killed in crossfire or bloodlust, in revenge for 1-2 settlers killed a week before.

The most populous tribes lived in the most fertile land – mainly along Australia’s coasts and major rivers. Where strangely enough, most modern Australians live today - especially in the colder, temperate and well-watered south east and south west corners. Eurasian diseases, much like in North and South America, brought about massive casualties in native tribes, sometimes even without having ever seeing Europeans – when explorers first crossed Sydney’s Blue Mountains, they were shocked to see tribes already long dead from disease. With loss of land and food sources to Europeans, and knowledge and leadership to disease, social cohesion broke down, and tribes collapsed. Dampier’s image of the miserable savage may have been total falsehood in his time, but for European settlers living close to the remnants of a tribe it was completely confirmed in their sightings of a half-dead people.