St. Augustine was overly influenced by his Manichaeanism. The Greek fathers were completely opposed to St. Augustine’s excessive rejection of free-will.
The Western Church suffered from an excessive reliance on St. Augustine rather than the broader view provided by the other Church fathers.
Which may be why the Orthodox church has been overrun by Islam and atheism in so many areas.
Relying on the power of God for salvation is vital in maintaining a strong church. When one relies over-much on one's own strength to achieve salvation, one is easily destroyed by other faiths which purport that same theology.