Exactly Qubic couldn't sustain it. Even during the attack you just had to wait for more confirmations.

My point was that for example Foundry alone could selfish mine Bitcoin already and it would be the same situation as Qubic and Monero. They have about as much hashrate as Qubic had at it's peak as with Monero. Just because they haven't done it yet doesn't mean they don't have the ability to. Incentives make it unlikely, but selfish mining inverts incentives. It's more of an economic attack.