They could confidently control everything and then carry out those tasks, but since they lacked such abilities and chose Gongsun Mo, it proved that things would not unfold as Gongsun Mo imagined. In the subsequent situations, it would lead to Gongsun Mo having to bear it all, including the very likely scenario of his backing force making him take the fall.
Neither did Li Fei think of using this incident to obliterate the forces behind Gongsun Mo. If they dare to stir up trouble in Jingcheng, he is not like the Feng Family or the Chu Family who think that outsiders must be inferior, or that they should lower their stance to share a slice of Jingcheng's power, even if it means aiming to replace it, at least at the beginning, they should act humble.