Elastic made a strategic mistake, and Amazon made the jerk move that was open to them.
Amazon built the product with the hope that it would continue to be developed with that license. What are they supposed to do with the license change? Just accept whatever Elastic said? I don't think you can blame them for taking the last version where they agreed with the license and continue to use and develop it. Sure, maybe making it open is a bit of a jab back, but even in isolation it makes sense for them.
They’re also switching out the license under everyone else. It’s maybe notable that elastics cloud offering was acquired at some point (it used to be found.io). I used to do elasticsearch consulting and I could name a few customers that will now have to reevaluate their product.
In contrast, a number of people here are acting as if AWS is totally in the wrong. But the only wrong here is Elastic making the mistake and then acting as if the whole thing is AWS' fault. No, if you license your software improperly that's on you, not anyone else.