This "financial crisis" was created by the republicans by making the post office do things no other agency has to do. It's fucking bullshit.
The step taken by the Postal Board of Governors to forgo the pension payments is meant to preserve cash and liquidity due to the Postal Service’s “ongoing, severe financial crisis,” Postal Service Chief Financial Officer Luke Grossmann said in an internal message to USPS employees. Officials have warned the USPS is on course to run out of cash by around February 2027.
Edit: Here is an article that explains it: https://www.govtrack.us/congress/bills/116/hr2382/summary