1) Hamstringing its finances: "The postal service faces unusual limits on its ability to manage costs, such as an obligation imposed by a 2006 law to 'prefund' a large portion of its retiree healthcare plan, instead of a more typical pay-as-you-go arrangement." Newman doesn't mention that the prefunding is an accounting trick used to understate the size of the federal budget deficit.
2) Making it obsolete: "Congress has ... micromanaged the postal service through a strict set of rules governing what it can and can't do while fulfilling its mandate of universal mail service."
3) Waiting until disaster is near: "The USPS has been seeking sounder finances and greater independence for several years, yet Congress has sat on its hands to the point that default seems likely and insolvency is even possible."
Dead Tree Edition: How Congress Bankrupted the Postal Service in 3 Easy Steps