One of the main things Amazon has going for it is that one can usually expect to see the whole gamut of competitive products, read helpful reviews, etc.
But when products are missing from the results for competitive reasons, the trustworthiness of the platform goes out the window.
So this may be a short-term beneficial strategy for Amazon but will surely backfire in the future. I'll be reluctant to buy more stock until the impact of the strategy becomes more clear.