Weird and a shame. Their stated reason was that their impact was "spread too thin". I don't know what that is supposed to mean. That was sort of the point of the program. I heard from a lot of nonprofits that while the AmazonSmile donations they received weren't massive, they still facilitated important efforts.
I hope they have an alternative in mind to replace it, rather than just nothing.
To Amazon's credit they are giving each nonprofit a one-time donation equal to three months of their 2022 donations to help them transition from the loss of the revenue stream.