they were smoking huge job growth numbers for NYCC and STC, back then the city of Toronto assumed for some reason that most office employment growth in the GTA would continue to happen in the city of Toronto (this was the early 80's.. the 905 was just beginning to be a thing), and the anti development crowd downtown wanted all the growth in the burbs of Metro Toronto. Thus the huge job growth numbers. Through planning and bad politics, transport planners most job growth in Toronto would occur in 4 centre, NYCC, STC, Etobicoke centre (around Islington), and York centre on the Eglinton subway at the Kodak lands. Of those two, NYCC and STC were considered to be the larger two. While NYCC somewhat succeeded, its employment is still roughly 1/10th of what it is supposed to be at right now according to those 1980's plans, York centre doesn't exist, then Etobicoke and Scarborough Centre are barely anything more than a particularly large cluster of condos.
The job growth largely still occurred, just downtown and in the 905. Developers struggled to justify building in expensive urban centres (higher land costs, parking costs, etc.) when they didn't have access to the centralized access of downtown. It then became the option of cheap land with cheap parking costs out in the 905, or expensive land and little parking in downtown with easy transit access. The 416 was generally considered a no-go.