What  does Prof. Hill mean by "nobody" in the context of this interview, and what does being a "nobody" entail?

Prof. Hill is the author of the book “Nobody: Casualities of America’s War on the Vulnerable, Ferguson to Flint and Beyond”, in which he examines the intertwining mechanisms that exclude vulnerable parts of the population, especially a lot of Afro-Americans.
 Concerning the Afro-American community Prof. Hill refers to Malcom X  who already stated that Afro-Americans were “the losers of democracy” as they had to face state violence for centueries and still have to face it today.

However, "nobodiness" does not only concern young black males but also members of the LBGT community, women, disabled persons as well as marginalized white men who lost their jobs due to technological progress and neoliberal politics.

According to Prof. Hill the feeling of nobodiness of vulnerable parts of the population results from the obsession with austerity and a neoliberal market logic as well as globalization, the feeling of many black people additionally from systematic racism.  (Prozeugma).

What socioeconomic factors does Prof. Hill maintain lead people to identify themselves as "nobodies"?

The neoliberal paradigm, the obsession of efficiency, the deregulation and globalization lead to nobodiness (Hypozeugma). In that context Prof. Hill refers to a politics of disposability which erases the vulnerable and gives them the feeling to be nobodies.  He applies this concept to young black males who suffer from systematic racism and over policing in their communities. Furthermore he applies it to a part of the white workers class that was fired, outsourced, and excluded from the labor market (Diazeugma).

 Why, according to Prof. Hill, have a certain subset of white people taken to identifying as nobodies?

According to Prof. Hill a part of the white population does not benefit from neoliberal politics and globalization. Thus, this part of the population is economically and socially disconnected and disaffectected, the wealthier part of the population more polarized (Prozeugma). The shutdown of factories and the progress of technology rendered them to nobodiness, a condition without political influence and perspective.

According to Prof. Hill these are tragically people who are vulnerable to rally around whiteness instead of rallying around labor despite of the common interests with the Afro-American community. In this context Prof. Hill draws an allusion to WEB Du Bois who already claimed that the end of slavery has been in the interest of white workers because slavery were outpricing their manpower. Nevertheless republican leaders such as Trump use the vulnerabilities of impoverished white workers to embrace the concept of whiteness, which is a concept of privilege and power that excludes many people a priori. Thus, instead of unifying those who are losing out from the current global economic situation they rally against each other on racial and political lines.