I think the hope was that the money would be used to support local cultural content/events since people in those enterprises have been hard hit by the COVID crisis.
Where are they buying the books? (sorry if the article mentions this, it's paywalled)
If it's independent stores, then I think that qualifies as a local enterprise hit hard by COVID, and fits in the spirit of the scheme, maybe even national bookstores can be considered thusly, too.
If they can give the money to Amazon, though, then maybe there's an issue.
More specifically, the article points out the money was supposed to be used to expose the kids to culture that they're not already exposed to. Instead, they're using it to buy more of the culture (magna) that they're already buying anyway.