They would have been able to object to ICANN when the other application for .amazon was put in.

Could also be a security issue. Creating one of those sites would surely help nefarious actors create amazon related scam sites. If amazon controls the TLD then only amazon can create .amazon sites.

They still don't need exclusive rights to the TLD. I doubt Brazil or one of the other eight countries was planning to create such domains.

I think the defensive aspect is underestimated.

I know from personal experience that carving out a clear online domain name is a lot harder with the expansion of tlds.

Also, I expect phishing sites will have an ever easier time registering convincing domains. So we're going to end up relying on browser blacklisting... not exactly an improvement for security.