Amazon didn’t block the ads for Apple, they allowed Apple to buy all of the ad space on their product page so they could decide what went there in order to combat counterfeit products and accessories from showing up— a big problem on Amazon. The question isn’t, “why is Apple allowed to do this?” The question is, “why isn’t everyone allowed to do this?” All companies should have the ability to do this, not just a few, and people should be upset with Amazon, not Apple, for cutting off everyone from being able to buy out the ad space on their own product pages.
And then there’s Amazon’s massive problem with counterfeit products which is what caused Apple to demand control of the ads on its product page in the first place.