In addition to its normal usages, (not nice, and has the meaning of), mean can also be used as a mathematical term to mean the average of a set of numbers. I always figured this was roughly the sense in which the word is being used in GMT.
Most people who pay attention to politics assume that George Soros is the largest financier of leftist election candidates. While he may have the largest non-profit funding network, Soros is not the person who spent the most directly helping candidates through superPACs or other organizations in 2016. That person is Tom Steyer, a former hedge fund executive who made his fortune in the fossil fuel industry. The Washington Post reported Steyer spent $66.3 million helping Democrats in the 2016 cycle, and the Washington Times reports that the final spend was north of $85 million.
George Soros is Hungarian-born American business magnate, investor, author, and philanthropist. He is a founder and chairman of Soros Fund Management and the Open Society Foundations. Soros was born in Budapest, Hungary to Elizabeth and Tivadar. In 1951 Soros earned a Bachelor of Science in philosophy and a PhD in philosophy in 1954, both from the London School of Economics. Hungarian-American financier, businessman and notable philanthropist, George Soros, has a net worth of $26 billion.