[Solar19]

Are you taking about the word "Defense" in Oshkosh Defense? Yeah, this isn't a military vehicle. It's a van, not some sort of modified Humvee or anything.

Oshkosh makes lots of vehicles and some civilian kit like fire trucks, air compressors, etc. They saw the opportunity and designed a van to fulfill the specs. Granted, bidding on government projects is likely in their comfort zone, but I would assume they won fair and square unless there was reason to believe otherwise.

The other two finalists weren't major car companies either, at least not in the US. Workhorse is a very small firm with just over 100 employees total, and Karsan is Turkish company I don't know much about.

The Renault Kangoo is probably too small for emerging USPS needs, though the existing postal vehicles are almost as small as the Renault. The USPS's core business is shifting to package delivery, instead of letter mail. E-commerce has changed the mix. They're the preferred shipping carrier for packages in the US, being generally less expensive than UPS, which is in turn less expensive than FedEx. Packages are bulky.

Also, I think it's irrational for outsiders (e.g. you and I and anyone not involved in the decision) to have strong opinions about the vehicle the USPS selects as the result of its contract and bidding process, much less make some sort of political inference from it. Most things aren't political. Mail delivery van procurement is rarely going to present a genuine opportunity for political insight beyond the usual mundane government procurement issues.