A single sequencer operating for a rollup is sufficient for security (safety), however it imposes a limit for censorship-resistance, uptime, and fair ordering. In order to prevent any potential issues, Citrea is working towards a solution that significantly reduces risks by allowing multiple sequencers to produce and finalize blocks with sub-second timing.
The consensus network between multiple sequencers minimizes the risk of censorship on the L2 level, reducing Bitcoin fallback force transaction count (thus reducing the need for users to force-transact). It also removes the need to trust the sequencer ordering, even it is for a short time, because now ordering is determined and finalized on the sequencer network with sub-second timing.
A Decentralized Sequencer Network can further reduce the costs of the rollup because it allows the posting of roots and proofs to Bitcoin less often, as the ordering is guaranteed and finalized on the L2 directly.