Complex sentence: In the 1970s, both Dynamo and Empor had died away to be replaced by BSG Chemie 70 Rostock but by this time, ice hockey in the DDR was very much a minority sport and BSG Chemie played very few games.
Split into simpler sentences: In the 1970s, both Dynamo and Empor had folded, to be replaced by BSG Chemie 70 Rostock. By this time, ice hockey in East Germany was very much a minority sport and BSG Chemie played very few games.