Their strong central government kept the Henians in line for quite some time. It functioned well as long as the court of the well to do did not interfere. The court was far more concerned with social etiquette and things like tea ceremonies
to really pay too much attention
As a result of landowners obtaining personal armies, the Henians ended up adopting a feudalist government type. The streets were no longer a safe place for people without personal bodyguards so it resulted in people giving up their own lands and goods in order for protection. The lords themselves needed protection so they hired their own personal samurai to keep them safe. Samurai are incredibly dedicated soldiers who would rather die nobly than live a long life. All of this barging and fear lead to the ultimate decline of the Henian.