Current market caps are not directly representative of how much fiat is either backing a coin or driving the total market. A $640B market cap for TRX would not be much of a stretch if blockchain takes off like it should and the total market cap surpasses say, $5T. I know it's hard to believe, but just for reference, the CMC in 2013 was $1B. This time last year, it was $70B. Know what happened from late Nov. 2017 to the beginning of January 2018? It shot up to over $800B. A lot of you like to perceive this as an everlasting crash, but you really need to zoom out and take a look at the whole picture.
People said it was impossible for Bitcoin to reach $1 with a market cap of even a few million dollars, let alone $100, let alone $1,000, let alone $10,000. It's trumped ALL of those and peaked at $19,000+/$300B.