How can the mainnet know that results submitted by a Rollup are correct? Many people can't answer!
Many fraud proofs use an interactive dispute process: both sides repeatedly narrow down the scope of their disagreement, and in the end, the mainnet only needs to re-execute one step to determine who is right.
The sequencer can determine the order of transactions; mature Rollups allow users to bypass the sequencer and force transactions through the mainnet, preventing transactions from being rejected indefinitely.
Cross-check information from multiple parties before deciding; don't just take one person's word for it.
$ARB 0.158(-3.6%)