He inherited an aging system that has been dogged with failures since the Iraq War began. The VA was crumbling in the 90’s and in spite of this fact, delivered good healthcare. It still does, despite serious shortcomings. The infrastructure has not been modified. The culture is Vietnam era. They are desperately short of mental health care professionals. And they lied.
Someone had to take the fall, and Shinseki fit the bill. A lot of conservatives never forgave him for telling the truth about invading Iraq. His troop numbers gave Donny Rumsfeld and Wolfy Wolfowitz the vapors. And when it turned out he was right, they hated him even more.
The VA needs money, resources, and a new culture. Firing Eric Shinseki did nothing to solve the problem.