Or the Occam's Razor explanation that they weren't thinking about it at all, because customers who shop based on Independent Bookstore Day are a very different, negligibly small customer base who weren't going to be spending their money at Amazon anyway.
I'm pretty sure C Suite and upper management took some under graduate courses at some point and all know about Occam's Razor. They probably hold meetings on how to use it to their advantage to continue to enrich the company.
Wasn't that already done for 20 years? If the remaining indie customers are not buying books from Amazon, as stated in the venn diagram comment at the top of this thread, they won't be affected by this sale.