The problem Decentralized Sequencers for Optimism rollup solves

Decentralization
Decentralization of sequencers is the prime goal of this project. Sequencers are a major centralization risk in the rollup space. This is compounded by the fact that the two of the most popular Ethereum optimistic rollups, Optimism and Arbitrum, are running their own centralized sequencers.

Censorship-resistance
Decentralized sequencers have better resistance to transaction censorship. For example, since optimism is an US-based project, it may need to censor transactions not compliant with OFAC rules of the US department of treasury. A decentralized sequencer is run by multiple entities across different countries so there's not a single point of attributability.

Fairness
It also enables fairness in opportunities for sequencing blocks. Anyone can join the decentralized sequencer network of nodes and get a chance to sequence (build) a rollup block and get rewarded by the network.

Fast L2 finality
We see one of the big benefits of distributed sequencer validation to give more (and faster) confidence to external actors like CEXes and bridges about the canonical chain, without having to wait for the sequencing window. It would also enable less secure light-clients that simply check the signature.

Interoperability (future)
We believe that cross-rollup sequencer interoperability is going to be an important milestone in the future. This effectively means that the sequencer network that we build for optimism can be extended for use by any other Ethereum rollup. This greatly improves the decentralized and security property of the network as whole.

Challenges we ran into

L1 bindings
Optimism (L2) uses abigen to generate go bindings for a smart contract deployed on L1. We had multiple issues generating and using these bindings to call methods on the L1 contract. We simplified the contract code for us to just get past it.