why 10 million s.f.?

I'm reading Eric Darton's book Divided We Stand and although I'm enjoying it, I'm still perplexed by the history and purpose of the towers. Were the three major players who initiated the project, Nelson and David Rockerfeller and Austin Tobin, motivated by a conviction of futurism? Why Yamasaki? Also, without Corbu, would the aesthetic of the tower and the superblock even existed?

The history of the development would make any red-blooded libertarian choke on his or her lunch. The blatant land grab by the Port Authority, the displacement of the last true port facilities to New Jersey, the hard cash subsidies, and the economic sketchiness of the plan are simply astonishing. And why so large?
I turn to Cool Hand Luke:
"Why fifty eggs?"
"Don't know, seemed like a nice round number."