I don't think it's sufficient to say "who cares about X" where X is what the President is attacking at the moment, because the consequences may be unforeseen, and go beyond the specific target. His goals are also unclear, which sows instability and uncertainty.

In this case, people reasonably suspect that part of the motivation is his dislike for the WaPo and Bezos, and that he wants to attack Amazon due to its association.

However, part of the process seems to be spreading non-factual information about the USPS. It's got to be nerve-wracking for the employees, thinking that this might be an indicator that the federal government is working on new ways to undermine them while pretending to "help".

Then too, Bezos is not the only owner of a newspaper which has or might criticize the President, so people are justifiably concerned about the implications of this vendetta for a free press.

All this is separate from whether the welfare of Amazon is particularly vital to a person.