It's money spent, businesses don't spend money unless they are confident some will be coming back the other way, especially if there is asbestos involved. There are lots of sites where demo will happen, then some delay causes it to sit idle for a while.
Also not to mention the reasoning that... why wouldn't they go ahead with it? It's just a senior's tower. It will definitely fill up, considering it's in a better location than probably any other seniors residence in the city (a short walk to nearly any service you could want)
they had been exiting tenants for a while, my guess is this was part of the process and now that the building is empty they can get underway with demolition. all part of the plan. cant see how a couple months after approval they would go full parking lot.