Yuan Zhen became a deposed provincial magistrate due to a combination of political intrigue, corruption allegations, and public dissatisfaction. His downfall was a result of a complex interplay of factors, including his own actions and the broader political context of the Tang Dynasty.

Yuan Zhen's deposal can be attributed to several key reasons. Firstly, he was accused of corruption, which was a significant issue during the Tang Dynasty. According to historical records, Yuan Zhen was known for his excessive taxation and exploitation of the local population, leading to widespread discontent. This corruption not only eroded his popularity but also damaged the credibility of the government. The Tang Dynasty government, under Emperor Xianzong, was particularly sensitive to corruption, as it threatened the stability of the empire. The data from the Tang Code, a legal compendium of the Tang Dynasty, reveals that corruption was a major concern for the government, with strict penalties for officials found guilty of such offenses.

Secondly, Yuan Zhen's political enemies played a crucial role in his downfall. He was involved in a power struggle with other officials, who were eager to remove him from his position. These enemies capitalized on his corruption allegations and used them as a means to weaken his influence. The political intrigue within the Tang Dynasty was intense, with many officials vying for power and influence. Yuan Zhen's enemies exploited this environment to their advantage, ultimately leading to his deposition.

Additionally, public dissatisfaction with Yuan Zhen's governance contributed to his downfall. The local population was suffering under his heavy taxation and oppressive rule. This discontent was further exacerbated by the fact that Yuan Zhen was seen as an outsider, having been appointed to the position from a distant province. The lack of local ties and his harsh policies made him deeply unpopular. The An Lushan Rebellion, a major uprising during the Tang Dynasty, also played a role in Yuan Zhen's deposal. As the rebellion gained momentum, the government was forced to reassess its priorities and remove officials who were seen as ineffective or corrupt. Yuan Zhen was one of the many officials who fell victim to this reassessment.

In conclusion, Yuan Zhen's deposal as a provincial magistrate was a result of a combination of corruption allegations, political intrigue, and public dissatisfaction. The Tang Dynasty government's sensitivity to corruption, the power struggles among officials, and the broader context of the An Lushan Rebellion all contributed to his downfall. The historical records from the Tang Code provide evidence of the government's efforts to combat corruption, while the political and social dynamics of the era further illustrate the reasons behind Yuan Zhen's deposal.