Complex sentence: The basic premise of this expensive project, that miasma spread cholera infection, was wrong; however, instead of this causing the project to fail, the new sewers succeeded in virtually eliminating the disease by removing the contamination.
Split into simpler sentences: The basic premise of this expensive project, that miasma spread cholera infection, was wrong. However, instead of causing the project to fail, the new sewers succeeded in virtually eliminating the disease by removing the contamination.