Why can't Xu Fengnian be proclaimed emperor?

Xu Fengnian cannot call himself emperor. In my opinion, there are two main reasons:

The first reason is that Xu Fengnian's fate is bumpy.

As the Prince of Northern Liang Dynasty, Xu Fengnian did not like to make plans on power and status, but preferred Jianghu life. All the relatives and friends around him left him one by one, which must have made him feel very painful and lonely. It is better to take wives and concubines to wander the rivers and lakes, stay away from the noise of the world and the complexity of government affairs, and seek a comfortable life.

The second reason is the end of the cold war and the exclusion of the imperial court.

In order to eliminate the Northern Mang, the 300,000-strong Beiliang Army was almost completely annihilated, which weakened Beiliang. Even if Xu Fengnian wanted to be an emperor, he was unable to fight against the imperial court.

Besides, the imperial court has always regarded Beiliang as a thorn in his side, and even if Xu Fengnian doesn't live in seclusion, the imperial court will not let him go. Xu Fengnian successfully resisted the invasion of the Northern Mang Army to the Central Plains, protected people's lives and made people live and work in peace and contentment. This is also a good thing he did before he retired, so it means a little retirement.