The usual things.... fear, ignorance and racism.

Racism and lack of bipartisan support were likely huge factors as other commenters said. There was also division between Indigenous people regarding the efficacy of the Voice to Parliament. Some saw it as a great step forward, others saw it as toothless or symbolic, others still believed it would delegitimise their sovereignty over the land. The Opposition latched onto this for their own gains I believe. Together with Fair Australia (conservative lobbying group) they dealed in fear, misinformation and distrust. They absolutely dominated over social media and took control of the narrative very quickly. This became a lot easier for them due to the cost of living crisis. Take a White Australian in the outer suburbs or rural areas, tell them to care about this thing they don't understand instead of their rising mortgage payments and cost of groceries, when the Opposition is feeding into their latent ignorance and distrust of First Nations people that all Australians have, and you've lost them already.

How much time have you got? I guess the biggest factor is that referendums are hard to pass in Australia, especially when the campaign becomes partisan. And this one was VERY partisan. But also Australia has a particular type of racist ignorance when it comes to our First Nations Peoples and our colonial history in general. We're now currently the only settler colonial nation that has not recognised its First Nations Peoples in their constitution. Settler colonialism is not a competition, but if it was Australia kind of wins the gold. I say that as a white Australian.

There's a lot of different views, many with some truths to it. I'll try to give an answer but please take into account my answer is quite bias too.

The question, unlike the title of the article, the actual vote is on

whether the Constitution should be changed to include a recognition of the First Peoples of Australia by establishing an Aboriginal and Torres Strait Islander Voice.

The problem is, how exactly or what exactly is an Aboriginal/Torres strait Islander voice. It's not like Australia is voting to not give these groups voting rights like many articles seem to suggest.

It's about what does this voice mean, do they have the power over government, can they stop laws, does it even help, whose even in it?

And there is no answer real answer, most answers I see are "it's about creating a voice" or "we want to see Aus support before putting into action" etc (this may have changed later but that was the initial info I was getting), so you basically asked the Australian people to vote into changing the consitution on a potential something? Which for many feels like a permanent change or an unknown thing.

So all the no side had to do was be like "oh if you don't know, then best to err on the safe side and vote no". "Who knows what this could do". "You can always wait and change it later".

Imo the votes would have been very different if it instead just asked "would you like to see an Aboriginal / Torres strait Islander voice in government" and not touched the constitution. Or if they just made the voice/team/group and showed Aus how helpful it was before asking them to change the consitution.

And (I'm prob showing more bias here) if the yes side didn't just call everyone racist who looked at the no vote (which I believe many are swing voters), it couldve provided enough time/listening to make changes to the argument that would change the voters. For example if they made it clear that it would just be used to support better decision making and help understanding etc. Though I can't be too harsh when many of the no side arguments felt objectively like lies.