There's a lot of semi-incorrect information here. With Optimism, there can be multiple L2 chains, by different "Chain Organizers". When you submit a transactio

There's a lot of semi-incorrect information here. With Optimism, there can be multiple L2 chains, by different "Chain Organizers". When you submit a transaction, you get a receipt from Organizer, a cryptographic promise that it will be included in future rollup. It means only Organizers can attempt to front-run, by adding a transaction before giving out your receipt. And users can always choose to use different Organizers, those that don't front-run. Since Organizers gain a small amount of fees, it doesn't make sense to be a bad, front-running Organizer.