Yeah what happens is fund managers buy stock that follow the ASX...

Yeah what happens is fund managers buy stock that follow the ASX 200. And then these funds then lend these shares to others for a fee that want to short them. There is a lending of shares to shorters who then flood the ASX with shares selling them driving the share price down. It's what happened with Polynovo. There was a very deliberate and targeted attacks in the company, 75 million polynovo shares have been shorted, so what happens. You need a catalyst. Such as a company that's at all time highs and has had a dent in their sales or perhaps they are in tech or haven't sold.much yet and are trading on future goodwill/expected sales. Then the shorters target that company, they borrow the shares from the funds. The funds get paid a borrowing fee and then if the shareprice plummets BRN could get kicked out of the ASX 200 and then these funds managers who hold the ASX 200 shares then need to sell those shares that the shorters then buy at the lower price. But they have put in a short position at the start of this targeting and benefit immensely from the lower price.
Brn is a target due to its high share price, in the tech sector and no real revenues yet trading on very high multiples. I am not saying it will happen I have no dog in the fight but BRN is a logical next target using this method
If you see short positions increasing over the next 6 months to around 10-12 % this is what is happening.