"a congressional mandate to prefund retirement health care benefits"
I'm not saying that's a bad idea in isolation. However if you're trying to make a political point that your enemy is a failure, merely force your enemy to do something sensible that no one else is forced to do, then when that destroys them, you can blame them for it, or something like that.
That was just round one. Here's round two of how to destroy the USPS, done in two simple quotes from the same story:
"In addition, it would give access to another $10 billion loan backed up by Postal Service property, which would have to be sold a decade later to pay off that loan."
"And individual Democrats and Republicans are united in their effort to prevent their own neighborhood post office or postal plant from closing."
Ta da! We require you to take out a loan, which you need because we forbid you from managing your own business, furthermore we also specifically forbid you to repay the loan. I'm sure nothing bad could happen in that situation LOL. I give 100% odds that this scheme will hit the fan as "proof of usps and bureaucrat mismanagement" when it is actually 100% the fault of congress meddling, of which at about 50% are trying to manufacture a political point to fit a predetermined agenda.
The problem with meaningless sloganeering is even if a slogan is generally correct, there will of course be outliers in opposition. This seems to be the case with the USPS. It would seem that blind faith based belief is so weak, the only way to enforce conformity is to intentionally sabotage a minor outlier.
The TLDR is they're being set up. (Edited to add, its the old game of take away authority needed to succeed, while leaving behind the responsibility of resulting failure. For a .gov, the USPS is actually pretty well managed, which is why its being targetted).