Yizhou itself is well-equipped with both civil and military talents. Although it lacks top-tier civil officials and military generals, there are quite a few second-tier ones, and their numbers add up. If they unite with one heart, supporting a single Feudal Lord is very easy.
Moreover, currently, Yizhou does not have a large number of incoming parties, and there is not much intense partisan strife. Liu Zhang holds his power in a way that doesn't stifle others, and the governance of both civil and military officials is quite harmonious.
After all, there are leaders among both the civil officials and military generals, and the leaders have fairly good characters. Although everyone has their own little calculations, preserving Yizhou remains the common thought of all.
This results in a peculiar situation where, clearly, everyone has their own ideas, but all the officials of Yizhou support Liu Zhang, including Wu Yi and Zhang Song among others.