Mr. Jannard was a billionaire way before that
Having a net worth of over 1 billion and having cold hard cash are two different stories. Net worth (tied to a company's stock price/earnings) can change daily. You can be a billionaire one day and then Enron the next. Cash is cash. You only get hit with inflation and taxes. If you have the 9 zeros in your bank account, the interest that you will get paid will more than make up for it.
And since he has held the company stock over 1 year, this is a long term capital gain. The cash he should receive when the sale of the stock goes through will only be taxed at 15%. You do the math, he is going one with almost 1.15 billion in his pocket - and he gets to stay chairman of the board and "chief mad scientist." Sounds like a really good deal for him.