Complex sentence: This reconstruction of the fortifications had serious negative consequences because it hindered economic development, which almost totally by-passed Minden; other smaller towns like Bielefeld and Dortmund laid the foundation for their greater subsequent growth.
Split into simpler sentences: This reconstruction of the fortifications had serious negative consequences because it hindered economic development, which almost totally by-passed Minden. During this time relatively smaller towns like Bielefeld and Dortmund laid the foundation for their greater subsequent growth.