Why did none of the Aborigines there notice the Aboriginal song was a con?

Andrew Bolt, Herald Sun (Australia)
"....After the film, Wadi took to the stage, having been introduced as a Pintjantjatjara man from Mutitjulu. He addressed the audience, answering questions about his culture before singing a song “in language”, a performance that brought some in the audience to the verge of tears...
In August this year, Wadi appeared in Sydney’s Downing Centre District Court, charged with 30 counts of fraud. Only this time, Wadi wasn’t Wadi, son of an “Aboriginal magic man” from Uluru; he was Dallas Gwilliam from Neutral Bay in Sydney. As soon became apparent, Gwilliam, who is 40, was not Aboriginal and had never served in the military. As part of the case against him, DPP lawyer Steve Higgins accused Gwilliam of having constructed “an elaborate web of lies”, a statement which, though true, seems dismally inadequate. Gwilliam’s con was ever-evolving and wildly improvisatory, a 20-year jazz solo of A-grade bullshit in which he had posed not only as Aboriginal royalty and a special forces veteran, but as a Shaolin monk, seeded tennis player, telco millionaire, martial arts expert, UN peacekeeper and Chinese racing-car driver."