Regarding applying to another university for PhD during the first year PhD program at a top research US university
Although more experienced heads may give alternative advice, my recommendation is to focus on what you want to research rather than the personal relationship reasons you have. 

Remember what the SOP stands for: Statement of Purpose, why are you pursuing a PhD?

Professionalism aside, ad hominem attacks are not the subject of interest when you meet with potential advisers: you are the subject, what you are interested in, where you’d like to go, how you would approach a problem or issue.