In 1927, Haspel becomes plant manager in Sindelfingen and concentrates on the reorganisation of the bodywork facility. A deputy member of the Board of Management under Wilhelm Kissel since 1936, Wilhelm Haspel becomes a full member of the Board of Management at the end of 1941. Although he is married to a Jewish woman, the company retains him, contrary to what the Nazi regime had in mind, and thanks to his competence, which was beyond doubt, Haspel becomes Chairman of the Board of Management of Daimler-Benz AG on 19 August 1942. At the end of October 1945, he is dismissed on the instructions of the American occupying authorities, but was rehabilitated in mid-1947. He is able to exercise his function as Chairman of the Board of Management again without any restrictions from January 1, 1948. He plays a decisive role in preserving and expanding the commercial vehicle division, is responsible for the relocation of passenger car production from Untertürkheim to Sindelfingen, and strengthens the export orientation of Daimler-Benz AG. In addition, he is a resolute advocate of a return to motor sports, which finally takes place in spring 1952. Due to his sudden death at the age of only 53, Wilhelm Haspel is no longer able to exercise this sporting and economic success.