You can only do that on centralized exchanges, which would mean that you effectively doxx yourself by shorting. Also the exchange will most probably seize your funds before you are able to withdraw them.
It's only doxxing if you can, you connect that large transaction to the attacker, but you can't unless I'm missing something.
At the height of the attack, Qubic (the company) paid people up to $3 in QUBIC for every $1 of XMR they mined through QUBIC, and they achieved around 33% of XMR's hashrate which was sufficient to mine the majority of blocks for a few hours.
If they were forced to buy back all those QUBICs they paid out, this might have cost them ~$100k/day. But thanks to the media attention it's likely that they didn't need to buy anything back and actually were able to emit more than they otherwise could have.
XMR needs to adapt -- switch to PoS, or ASICs-based POW, or a hybrid of both.