Sybil detection. There are various methods.
There is criticism over how Arbitrum did the sybil detection in this case, but it is not that difficult to identify clustering unless people take serious (expensive) privacy measures
Did you read the bit where I explained that it was similar to getting a four year old to use a £1 coin to buy something, but that didnt mean that they were able to do options trading on derivaties futures? Optimistic roll-ups are not rocket science, but they do require a basic understanding of both crypto in general and ethereum architecture in particular.
No, you are not.
In the beginning there was Offchain Labs, a company established in 2018 to research optimistic rollups. In 2021, they raised $120m in seed funding from venture capitalists to build an optimistic rollup and established the Arbitrum Foundation, a not for profit subsiduary of Offchain Labs to oversee the development and governance of Arbitrum, the OR that they were building and appointed the directors.
The Arbitrum Foundation has now taken governance away from Offchain Labs and offered governance rights to approx 625k people that it believes can collectively govern the platform better than a subsiduary foundation of a company. Some of these people have sold their governance rights.
Nansen.ai has a pretty good write up on it if you'd like to know more
Nansen aided in the development of the Arbitrum airdrop distribution, which is supported by on-chain data analyses facilitated by Nansen Query.
www.nansen.ai
Maybes do a bit of research first next time to understand first rather than starting from the premise crypto is bad, therefore a bad thing that I can think of happening in crypto must be the case?