The issue "right now", is that it seems the entire crypto space is literally a house of cards/dominoes (pick your analogy).
A month ago, an attack was made on Terra, which crashed Luna. Celsius had significant Luna holdings, so they fell taking their CEL coin with it. 3AC had big holdings in CEL, so it's fallen. The market is extremely undiversified, so any crash is extremely contagious to other players since they are all invested in each other's "technology" (the most common holding for any particular digital currency fund is other digital currency).
The business strategy of Microstrategy for instance, is basically BTC price speculation. They bought lots of bitcoin, took a loan with their BTC as collateral, then bought more BTC with that money. So what happens when BTC falls below their entry price? Both their investment and their collateral are now underwater. They are in a very precarious situation if BTC falls meaningfully further.
As for Tether, I can only imagine they are invested in/can manipulate BTC because why not? They can basically prop up the price (and it's been researched by some that they may in fact have been doing that) by creating Tethers out of thin air. And even if they aren't just creating Tethers, if they just merely invest in BTC in an appreciating market, they get 1 USD, put it in BTC which becomes $3, then they redeem the 1 Tether and net $2. It all works as long as BTC keeps appreciating. It all falls apart when it goes the other way. So their 1 Tether is now worth 50 cents, but they still have to redeem that 1 Tether for 1 USD.
The floor on a potential crash is deep, because everyone depends on everyone else being solvent, and that solvency depends on an ever-appreciating bitcoin. But Bitcoin is going the other way. Luna was the #7 most valuable crypto not too long ago, and it went to zero in 24 hours. Imagine the French Franc, British Pound or German Mark go to zero in 24 hours. It would be catastrophic. That type of failure just doesn't happen with fiat.
Crypto is make believe money. Play stupid games, win stupid prizes.