The reason the charts track fairly close, and why volume has traditionally been so high in MSTR, is because of arb shop bots that are constantly buying or selling MSTR to take very small profits in price discrepancies in what they believe the nNAV should be in MSTR vs BTC spot price and futures prices on different exchanges.
As more and more volatility comes out of BTC, and as more fomo retail traders leave MSTR to chase the next hot stock (CRCL, COIN, HOOD, etc), fewer arb shops are as interested in devoting capital and resources to MSTR.
Overtime this will also lead to mNAV contraction as fewer arb shops are competing for the same intraday, and even intra-minute, snipes.
The mNAV for MSTR has now been under 2.0 for several weeks, and continues to slip lower over time. An mNAV under 2.0 kills the narrative for MSTR because there are safer Bitcoin ETFs that offer 2x leverage and have zero debt and zero shareholder dilution. In fact, if you read a MSTR prospectus for one of the STRx offerings, you'll see that MSTR recognizes this and identifies it as a threat to their business model in the disclosures and risks section.
The Chanos short position is simply a bet that the mNAV will continue to slip over time and that slippage will lead to an ever larger pricing discrepancy between BTC and MSTR. He is doing what the arb shops have been doing, except on a much larger scale and over a longer period of time. And he is using Saylor's model for raising capital (selling MSTR stock) to fund the operation. So far he has been right: The mNAV has fallen around 22% since he first opened his short position.