The five major families in Capital City are all top-tier families.
Never mind that the Dongfang Family could easily solve Zhu Bufan's problems with just a word, any of the five major families in Capital City could comfortably resolve the issues Zhu Bufan is facing right now just by speaking up on his behalf.
After all, the Yuwen Family is nothing but a second-tier family.
In the melting pot of Capital City, it's quite easy for a first-tier family to eliminate a second-tier family.
Of course, in Capital City, unless absolutely necessary to the point of eradicating another family, under normal circumstances, these families wouldn't engage in such conflicts.
After all, this is Capital City, located right beneath the emperor's feet. If you want to eliminate a family, you'd have to do it covertly; openly doing so would prompt the ruler to intervene.
How he would intervene depends on how severe the issue you've caused is.