My post was uninformed and misleading. I just found the linked article, which says that in April 2020, the fed started counting savings account balances in M1 money supply for the first time, explaining the 500% spike at that time.
I’m baffled that they’d just trash the M1 chart like this. It’s now useless. If I did this at my job, I’d be fired.
https://fredblog.stlouisfed.org/2021/05/savings-are-now-more-liquid-and-part-of-m1-money/