For money funds:

Generally, banks have to face performance appraisal at the end of the quarter, and one of the most important assessment points is the amount of deposits. In order to complete the assessment, banks are generally desperate to pull deposits from enterprises and find large households to pull deposits, and at the same time raise the deposit interest rate accordingly. If the amount of funds is large, the bank will give a particularly high deposit interest rate (generally, you can't see such a high deposit interest rate when you go to the bank business hall).

Therefore, the money fund can increase the rate of return at the end of the quarter to absorb deposits, and then go to the bank to earn higher interest income.