They did not lose as much as you think. Remember, they have been getting ad revenue for the last 6 years. I won't get into a finance lecture, but the sale included cash and stock. Not only that, the money they made from the boost in their price per share when they bought myspace more than covers any loss you think they may have incurred on selling this company. Things are much more complicated than a straight "buy-sell". If someone bough it for 580, then sold it a month later for 35, then you could say that they took a major loss. But this is not that cut and dry.
You really think they made even $100 million in any of the 6 years?
In March 2011, market research figures released by comScore suggested that Myspace had lost 10 million users between January and February 2011, and that it had fallen from 95 million to 63 million unique users during the previous twelve months. Myspace registered its sharpest audience declines in the month of February 2011, as traffic fell 44% from a year earlier to 37.7 million unique U.S. visitors. Advertisers have been reported as unwilling to commit to long term deals with the site.
In late February 2011, News Corp officially put the site up for sale, which was estimated to be worth $50–200 million. Losses from last quarter of 2010 were $156 million, over double of the previous year, which dragged down the otherwise strong results of parent News Corp
You have to think if they received $900 million from Google and still can't turn a profit something is wrong. CEO and COO are making money but the company itself is loosing value. More is going out in development than in from advertisements