I guess the new Bitcoin volume comes from the new buyers, not just new buyers but huge whalesj, probably there are people with public influence. Remember the time when BTC dumped to 3000 when it was hit by China fake news? Many people bought Bitcoin. Another reason, many hedge funds are now invested to Bitcoin.
The marked cap for BTC have increased from 60 to nearly 120b$ since september. In the meantime, the total market cap (BTC excluded) is somehow stable, only 10b$ have gone out of altcoins in the same period.
Where do you think the money that goes into BTC comes from? Margin trading? New money?
Do you know something by fact and a link that can support it