Complex sentence: Although Greenway won a landslide majority in this election, he was unable to fulfill his election promise for the development of local railways--while losing its official monopoly, the Canadian Pacific Railway was still the dominant line in the region, and transportation costs remained high.
Split into simpler sentences: Although Greenway won a landslide majority in this election, he was unable to fulfill his promise for the development of local railways. Though losing its official monopoly, the Canadian Pacific Railway was still the dominant line in the region, and transportation costs remained high.