Uh that's an accounting change iirc - they included some category worth 10 trn in M1 on that cut-over day, 10 trn/day slope is not an actual change in money supply.

Edit:

> Before May 2020, M1 consists of ... (3) other checkable deposits (OCDs), consisting of negotiable order of withdrawal, or NOW, and automatic transfer service, or ATS, accounts at depository institutions, share draft accounts at credit unions, and demand deposits at thrift institutions.

> Beginning May 2020, M1 consists of ... (3) other liquid deposits, consisting of OCDs and savings deposits (including money market deposit accounts).

> Seasonally adjusted M1 is constructed by summing currency, demand deposits, and OCDs (before May 2020) or other liquid deposits (beginning May 2020), each seasonally adjusted separately.

This means the balance of all savings accounts was added to M1 beginning may 2020. If you want to look at "money printed", look at M2. AIUI the definition of M2 was not changed that date and you can indeed see some ~2 trn covid stimulus spread out over a few months in M2.