Mind you, Otto Hahn represents not him alone, but does include Lise Meitner and Fritz Straßmann too. They were pioneering nuclear research in the late 1930s along with Fermi, and were the first to discover nuclear fission. His background was indeed chemistry, but his main research was focused on radioactive research, notably radioactivity and radiochemistry. As such I've been the driving force to include his team as a nuclear research team. Giving it the chemistry trait is overkill IMHO, as there were better labs (with much larger staff for starters). In contrast, nuclear research was still in it's infancy, so pioneering work.
In 1938 most Jewish researchers were trying to leave Germany, and so did Lise Meitner, who deserves half the credit for the groundbreaking work regarding nuclear fission (although Hahn got the Nobel laureate for it). This meant two things: the team was hurt badly in it's researching capability, and Hahn carried on with the results of their nuclear fission findings. He never got involved in military use of nuclear physics (nor wanted to). As nuclear research discovery takes a definite military swing from then on (Einstein's letters to the president), his team is dropped from the roster from 1939 onward.
Werner Heisenberg (remarkably having a Jewish background) then takes over the baton. I still consider him to be overpowered as a nuclear research team, as his main area of expertise was quantum mechanics, and the efforts of his research team and others (Heereswaffenamt Versuchsstelle under Kurt Diebner, Reichsforschungsrat amongst others) weren't really cooperating between each other, but rather competing against each other. As such the HWA might actually be a better pick there. But Hahn (and Meitner) deserve their spot in early German nuclear research, which is the driving force for their inclusion.