This is not some new development. I think politics has clouded many people’s memories and judgements.
The USPS has been struggling for decades - at least since the 1980s. It had a near monopoly of written communication until then with a few high priced competitors for fast short messages (Western Union, Telex, etc). It was financially self sufficient with limited indirect subsides and support.
Then the fax machine arrived, then the overnight delivery services, then email and the internet. These developments ate into USPS’s business model which required huge volumes to support a vast and expensive infrastructure. For a time the rise of junk mail provided some relief but even that waned in recent decades.
Managment of the USPS was unable to deal with these changes for a number of reasons including government mandates and an inflexible unionized workforce. One persistent problem was huge pension liabilities arising from labor contracts. But the key issue was the high costs and diminished demand.
It has been bailed out several times most recently in 2012. In the next few years another bailout will be needed or perhaps bankruptcy. A long-term solution would require a politically sensitive restructuring possibly including privatization. Many other countries have either completely or partially privatized their postal systems with generally good results.