For those of us who did not read the book, why did Francisco basically swindle people’s money before nationalization of the San Sebastian Mine?
Francisco didn't swindle anybody. He was teaching the looters and moochers a lesson, and the tuition paid for that instruction was the value of their investment.
People like Jim Taggart, Orren Boyle, etc. bought into the mine project only because it had the D'anconia name behind it. In Francisco's view, they were merely piggy-backing on the fruits of his mind.
When pressed further, Francisco's response was beautiful. Basically, he said "What's your problem? For months, I paid men good wages, I built schools, I built housing for all these people. I was doing what you expected producers like me to do. And now you come whining to me because you lost money?"
Another part of the plot not fully explained was the relationship of John Galt, Ragnar (the Pirate) Danneskjold, and Francisco D'anconia. They were the three prized students at Patrick Henry University, and they were caught in the vortex of the conflicting ideologies of Dr. Robert Stadler and Hugh Akston (Michael O'Keefe at Akston's Diner). If you'll recall, John Galt was drinking coffee at the Diner when Dagny first met Hugh.
Drat, I'm definitely going to re-read Part One in preparation for this weekend's trip to the theatre!