A lot of times I think of if you really want a simple mental model for understanding how modular blockchains work, it's really the combination of data availability sampling and fraud slash validity proofs. In a monolithic chain every node has to re-execute every transaction and Clearly that doesn't scale because as more transactions are Sort of processed at the same at the same amount of time. The whole idea behind roll-ups is that essentially it's a way of Knowing that the execution is valid Without having to re- execute every transaction yourself.