Complex sentence: Whether it was worth the money to complete the Trent was a matter of great debate, and ultimately completed due to it being one of the key election promises that led to Laurier's election win in 1896.
Split into simpler sentences: Whether it was worth the money to complete the Trent was a matter of great debate. It was ultimately completed due to it being one of the key election promises that led to Laurier's election win in 1896.