Agree with
@PolyRob, changes should be slow and go up and down with the fed funds rate. I was getting north of 5% with CIT Bank for a while, and it was 4%+ until very recently (now is 3.85%) but the changes were slow.
Note that sometimes companies do pull a fast one- maybe that happened to you? Capital One monkeyed around with their products and now there's a class action lawsuit against them. They slashed the interest rate on their main HYSA offering and made customers manually open and move their money into a new account to keep getting the high yield. I'm sure hundreds of thousands of people never noticed and or took several months before they realized what had been done to them. That was, I'm sure, their plan... and that's when I left them for CIT.
Another savings option is putting money in a U.S. treasury index fund- the yields aren't that much different for medium term bonds than HYSAs at this point and you don't pay any federal income tax.