I'm not sure why you're confused because the first sentence of the article literally says:
Australians have resoundingly rejected a proposal to recognise Aboriginal people in the country’s constitution and establish a body to advise parliament on Indigenous issues.
Which sums up why they were trying to make this happen, which also sounds like they don't have an official group of Indigenous peoples advising the government on anything that is an Indigenous issue, which is super bad.
I got as far as "Gatorade bottles labelled in Mandarin" in the summary to know that it's shotty journalism lmao