Another way to summarize would be that rising costs made it almost certain that the total price tag was going beyond the scope of the agreement, including the agreed upon contingency amounts. CSEC agreed to take on further cost overruns in exchange for removing CMLC from the project - letting CSEC focus on what they want while eliminating weak revenue generators like the practice/community rink. Then costs were even more than they could stomach so they found a good excuse to pull the plug while passing the buck.
A few issues overall:
1. Several significant costs were excluded/obfuscated to achieve a nice simple 50/50 infographic (land value, insurance, land options, demolition, etc.). The deal wasn't awful, but IMO it was too generous from the city, and they pissed away their best opportunity to extract a few final concessions when they...
2. ...rushed to vote before summer break. With a little more review and debate they also may have been able to identify and avoid pitfalls like the roads/sidewalks issue. And given the pace of the project to follow, it seems the urgency to get the vote done was false...almost as if they knew it wouldn't stand up well to scrutiny.