Question About Volume Of The Total Market Cap

This is probably a complete noob question, but I've only been observing the Crypto Total Market Cap chart for a couple weeks now.

Generally what I've seen is that as the total market cap goes up the trade volume goes up. Not until this week have I seen those two indicators diverge into opposite direction. I hoping someone has some past insight on what this has meant during previous bull runs. My assumption is people are taking their coins off exchanges and into safer storages as we see the market going up. This could be a completely inaccurate read, I'm just scratching my head on why were seeing lower trade volume when the market is boomin'