How can the ETH blockchain size decrease?

There was a huge decrease in the Ethereum blockchain size on or about January 26 2022 (https://ycharts.com/indicators/ethereum_chain_full_sync_data_size#:~:text=Ethereum%20Chain%20Full%20Sync%20Data%20Size%20is%20at%20a%20current,from%20982.41%20one%20year%20ago.)

It went from about 1.2 TB to 526GB. How does this happen if the chain is continually growing from genesis and sharding has not been implemented yet?