Given that all of these Delta cases came from indian nationals fleeing india for other nations and then reportedly refusing to self isolate (especially in sydney and melbourne), it has now come to light that the Indians have been lying about COVID positive passengers arriving in other nations.
I reckon what's happened is that the COVID positive indians bribed the officials to be allowed on the flights and given the laissez-faire inshallah 'pay you back next life' attitude of indians, they have allowed COVID-Delta passengers to infect the rest of the world. That's exactly how the latest cases have come about in australia for this recent wave in australia only came about when the government started allowing repatriation of indian nationals back into australia, limo driver or no limo driver.