From the description of the little Taoist from Ziyun View, Xiao Chen could almost confirm that Yun Zhen had possessed Ma Zhenghua, also known as Xuanxu Zi, and then renounced monastic life, changing his name to Ma Yi.
Although he had left behind Cultivation Techniques for the Yu Xiao Sect in the past, he had never left any technique for possession.
This meant that Yun Zhen's Cultivation Techniques originated from the Earth's indigenous Cultivation methods, which were not much related to him.
However, given the harsh and challenging cultivation environment on Earth, Yun Zhen had spent his entire life just reaching the threshold.
Therefore, he had to use some extreme methods to sustain his lifespan and enhance his Cultivation Level.
Such as possession and using cauldrons.
Xiao Chen would not stand on a moral high ground to judge Yun Zhen's actions because such survival of the fittest scenarios occur every day in the Cultivation World, and he was long used to it.