Fictional Rollup Attack

Layer 2
3
  1. Your “attack” seems to apply to not just optimistic rollups, but zk rollups and in fact any smart contract as well.
  2. I suggest you read this design paper, specifically section 8. It describes a not-well-known scheme for preventing Sybil nodes from presenting fake information, instead requiring a majority of computing power to be dishonest.
  3. The rollup’s state root can be emitted as an event or even stored in Ethereum state. This can be queried with no possibility of forgery (see section 7 of the above linked paper). Please study how optimistic rollups work, because they don’t work as you described.