Cleveland House on Young Avenue in Halifax has been torn down now too. It was an estate that belonged to the family of the US president Grover Cleveland (his ancestors originally settled in Halifax in the 1750's before back and forth between the US; the last owner was also named Grover Cleveland but it was a different Grover). It was built circa 1900 so it wasn't really considered a major heritage property but it really contributed to the heritage context of the area.
How did this happen?
1) A developer bought the property with the intention of converting the old house to apartments plus add new houses on the large lot.
2) Protests start over the demolition. NIMBYs complain about the apartments.
3) Developer demolishes building to avoid political problems. There are no demolition controls so this is the path of least resistance. Now his life is easier because his development proposal will be compared to a lot that he has an incentive to make as ugly and unpleasant as possible.
Back in the 90's there was a similar situation with some Victorian houses on Robie Street and apparently the developer painted them to make them as ugly as possible before finally demolishing them. Then NIMBYs bitterly fought any development of the site so it sat empty for 20 years.