All 2nd layer transactions are stored on the 1st layer.

The first layer does the required step of "ordering" the transactions in a decentralized system. Without this ordering step, different nodes would begin disagreeing about the order in which things happen, because they would see new transactions at different times (and this would be problematic, because then someone could spend their money twice). The whole point of block producers is to choose some particular node in the network who gets to order recent transactions for a given period of time (the current block).