So the problem was that Nirvana's Oracle Feed, that reported the price of ANA, was manipulated into showing a market price higher than was purchased by the exploiters. Who then sold their ANA back at the higher price for USDT, thus making a profit.

So how was the Nirvana Oracle manipulated to report a higher price for ANA? My guess is that the large purchase was enough to push the price higher (by 35%) and make the flash loan transaction profitable.