Why does swapping in L2 cost so much more than mainnet (L1)?

I was under the impression that swapping coins in L2 should be cheaper, but instead it cost more than 3 times.

Swapping in L2 (Arbitrum) for 5 Eth into USDC costs $22.37

Swapping in mainnet for 5 Eth into USDC costs $6.73

L2 Arbitrum swapping 5 Eth to USDC

Mainnet swapping 5 Eth to USDC