Amazon is an extremely visible American company, hitting their assets carries a symbolic meaning even if the DoD wouldn't have anything running on that datacentre at all. Iran's trying to transmit a message of "we can destroy your stuff too", trying to impact the general US feeling of invulnerability.
I don't think it'll work, but they might as well try I guess.
I don't think it'll work, but they might as well try I guess.