I wasn't aware of Monero's current situation and I'm fascinated that explicitely going for CPU mining over ASIC mining wasn't enough to protect their network from centralization. Funnily enough requiring ASICs makes a 51% attack more costly, given that in a situation of complete market obliteration a CPU mining attacker could reuse/resell their hardware for other purposes whereas an ASIC mining attacker would be left with a pile of worthless bricks.
This is probably why I think no one would dare to do the attack. But recent developments actually give us a hint that it's not impossible if someone wants to spend billions of dollars on it. As Qubik said, they have no intention of taking over the Monero network and manipulating it, but they did it for testing purposes and wanted to prove that it's actually possible.
Do I think the IOTA co-founder would dare to do it? Nope. I don't think he would plan something like this, as it would be very expensive for him. But we never know, there are a lot of stupid people who could be interested in wasting their money.