The timing doesn't line up - the USPS has been under attack since well before 2017. This reason might be reinforcement, but it can't be part of the core rationale.

And, honestly, there are "politicalish" scandals like this pretty frequently - I don't know if you recall the uproar about the IRS targeting conservative groups a few years back[1].

1. Which was, for clarity, disproven after the fact https://en.wikipedia.org/wiki/IRS_targeting_controversy