Java/C++/Python/Ruby/Go/Perl/Scala, even Rust, are used in Amazon for various projects. What might be true is that, consider how critical your service would be, the more it is, people will lean towards to more conservative/mature/enterprise-ish languages, not exotic ones, because that inherently means risk. And Java is the go-to option under that consideration, just because, it is Java, the least controversial choice if you had asked me.

But Amazon comparing with other companies I worked with, except extremely small startup, where tech guidance is like non-existent, the least restrictive when it comes to languages. It fits the Amazon's self perception, it is pragmatic, non opinionated, moral-agnostic. It cares about customer, because customer means potential of eventual profit. However you achieved that, is not Amazon's concern.